Merge #30: feat: add draft ADRs from PR #16 for review

64a6c62 feat: add draft ADRs from PR #16 (Cameron Garnham)

Pull request description:

  This PR adds the draft ADRs from PR #16 to the `docs/adr/draft/` folder for review and potential integration.

  ## Changes

  - **ADR-009**: Proposal to Adopt a Modernized Automation Toolchain
  - **ADR-010**: Proposal for a Test-Driven Implementation and Structure
  - **ADR-011**: Proposal for Perl Coding and Security Standards
  - **ADR-012**: Proposal for Meson Build System Principles and Conventions

  ## Context

  These ADRs were originally proposed in PR #16 but were copied to avoid conflicts with the existing ADR sequence. They are placed in `docs/adr/draft/` for review and potential integration into the main ADR sequence.

  ## Author Attribution

  Original author: Cameron Garnham (@da2ce7)
  Extracted from: PR #16

  ## Review Notes

  - ADRs have been renumbered from 004-007 to 009-012 to avoid conflicts
  - Internal cross-references have been updated to maintain consistency
  - Markdown lint issues have been fixed for better readability
  - Content remains unchanged from the original proposals

  Related to PR #16

ACKs for top commit:
  josecelano:
    ACK 64a6c62

Tree-SHA512: ccc33b16436af47647e793b925cbd46da8c92c422ea8a204dcfe70b9f8b7217d8ac26d7c968ad7a5da14e1dc1dfd73ec37683688d8f7b0fd37aea0b6203b3864

Author: josecelano

docs/adr/draft/009-adopt-modern-toolchain.md

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+### **ADR-009: Proposal to Adopt a Modernized Automation Toolchain**
+
+- **Status:** Proposed for Review
+- **Date:** 2025-07-09
+- **Proposer:** Cameron
+- **Reviewers:** [List of project maintainers/core contributors]
+
+#### **1. Context and Problem Statement**
+
+The project's current automation toolchain, based on `Makefile` and POSIX-compliant shell
+scripts, has provided a simple and conventional interface for developers. It is pragmatic and
+effective for its stated purpose.
+
+However, as we formally adopt the Twelve-Factor App methodology for the application itself, an
+analysis of our automation tooling reveals a philosophical misalignment. Specifically, the
+current tooling does not fully adhere to the principles it helps enforce:
+
+1. **Implicit Dependencies (Violation of Factor II):** The toolchain implicitly relies on the
+   existence and version of system-wide tools like `make`, `awk`, `grep`, and `curl`. Their
+   presence is not explicitly declared or verified in a manifest, leading to a non-deterministic
+   setup environment.
+2. **Blurred Build/Run Stages (Violation of Factor V):** Running a command like `make apply`
+   mixes infrastructure planning, building, and execution. There is no distinct "build" or
+   "setup" stage for the automation logic that validates its own dependencies before running.
+3. **Brittle Logic:** The current shell scripts rely on parsing the text output of command-line
+   tools (e.g., `virsh domifaddr | awk ...`). This creates a fragile contract that is less
+   stable across OS versions than using a formal, versioned API.
+
+This proposal seeks to address these shortcomings by evolving our automation toolchain to be a
+first-class, Twelve-Factor-compliant component of the project, thereby increasing its long-term
+robustness and maintainability.
+
+#### **2. Proposed Change**
+
+It is proposed that the project adopt a new technology stack for its automation, based on the
+following core decisions:
+
+1. **Adopt Meson as the Unified Automation Interface:** Meson will serve as the primary
+   user-facing tool for running all project tasks. It will provide a single, declarative entry
+   point for developers and CI/CD systems.
+2. **Adopt Modern Perl for Core Automation Logic:** The imperative logic currently in shell
+   scripts will be migrated to a new, structured Perl codebase.
+3. **Adopt a "System-Package-Only" Dependency Policy:** To ensure maximum stability and a
+   simple, curated "supply chain," this proposal mandates that all Perl module dependencies be
+   fulfilled **exclusively through the system's native package manager** (e.g., `apt install
+   libsys-virt-perl`). The direct use of language-specific, uncurated package managers like
+   `cpanm` will be explicitly disallowed in the project's setup and CI workflows.
+4. **Establish a Stable Target Platform Benchmark:** All tooling and dependencies will target
+   versions that are officially maintained for the **current Debian Stable release**. This
+   includes packages from the official `backports` repository, as they are specifically compiled
+   and certified for use with the stable base system. The critical guiding principle is: _Is the
+   package officially provided for Debian Stable by the Debian maintainers?_
+   - _As of this writing, this sets our target versions to **Perl `5.36.0`** (from `bookworm`)
+     and **Meson `1.7.0`** (from `bookworm-backports`)._
+
+#### **3. Rationale for Proposed Change**
+
+This strategic evolution will bring our automation toolchain into stronger alignment with the
+Twelve-Factor methodology and yield significant long-term benefits:
+
+- **Explicit, Verifiable Dependencies (Factor II):** The `meson.build` file will serve as an
+  explicit dependency manifest. It will programmatically check for `perl`, `opentofu`,
+  `libvirt-client`, and all required `perl-*` packages. This provides a single, deterministic
+  command (`meson setup`) to validate a contributor's environment, failing hard and early with
+  clear error messages if the environment is incorrect.
+- **Clear Build/Run Separation (Factor V):** The Meson workflow naturally separates our
+  processes. `meson setup` becomes our distinct "build" stage, which configures the project and
+  validates all dependencies. `meson test` or `meson compile` becomes the "run" stage,
+  executing tasks in a pre-validated environment.
+- **Increased Robustness and Maintainability:** Migrating from brittle text-parsing in shell to
+  using formal Perl modules (like `Sys::Virt`) allows us to depend on more stable, versioned
+  APIs. Perl also provides superior error handling, data structures, and code organization,
+  which will make the automation easier to maintain and extend.
+
+#### **4. Scope and Relationship to Other Proposals**
+
+This document's scope is strictly limited to the **strategic decision to adopt Meson and
+Perl**. It establishes the core "why" and "what" of the change.
+
+All further details are explicitly deferred to subsequent proposals, which will build upon this
+foundational decision:
+
+- **Implementation Strategy & Structure (`ADR-005`):** Will detail the "how" of this migration,
+  including the specific repository structure, the plan for an atomic cutover (a "flag day"
+  migration), and the deprecation of the `Makefile`.
+- **Coding & Quality Standards (`ADR-006` and `ADR-007`):** Will define the "rules of the road"
+  for the new Perl and Meson codebase, including mandatory pragmas, security hardening, linting
+  policies, and style conventions.
+
+#### **5. Consequences and Acknowledged Trade-offs**
+
+- **Primary Benefit:** The project's automation tooling will become a more reliable,
+  maintainable, and professionally engineered component, in full alignment with the principles
+  it helps to deploy.
+- **Acknowledged Trade-off 1: Loss of "Zero-Prerequisite" Setup.** The single greatest
+  trade-off is sacrificing the convenience of `make` being pre-installed. A contributor's first
+  action will now be to install the Meson/Perl toolchain via their system package manager. This
+  is a conscious decision to prioritize explicit, verifiable correctness over "zero-setup"
+  convenience.
+- **Acknowledged Trade-off 2: Dependency on a Curated Ecosystem.** By committing to system
+  packages benchmarked against Debian Stable (including its official backports), we gain
+  stability at the cost of immediate access to bleeding-edge tool and library features. This is
+  a deliberate choice to favor long-term stability and reliability.
+
+#### **6. Next Steps**
+
+If this strategic proposal is accepted, the maintainers will proceed with a formal review of
+`ADR-005`, `ADR-006`, and `ADR-007` to finalize the implementation plan and quality standards
+for the new toolchain.

docs/adr/draft/010-test-driven-implementation.md

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+### **ADR-010: Proposal for a Test-Driven Implementation and Structure**
+
+- **Status:** Proposed for Review
+- **Date:** 2025-07-09
+- **Proposer:** Cameron
+- **Reviewers:** [List of project maintainers/core contributors]
+- **Depends On:** [ADR-009: Proposal to Adopt a Modernized Automation Toolchain](./009-adopt-modern-toolchain.md)
+- **Supersedes:** [ADR-001: Keep Makefile at Repository Root Level](./001-makefile-location.md)
+
+#### **1. Context and Problem Statement**
+
+Following the strategic decision in `ADR-004` to adopt a Meson/Perl toolchain, we must now
+define a concrete implementation plan. A simple one-to-one replacement of scripts would fail to
+capitalize on the full benefits of the new toolchain and could lead to a disorganized codebase.
+
+This proposal addresses the "how" and "where" of the migration. It recommends a specific code
+structure and implementation methodology designed to maximize the reliability, maintainability,
+and testability of our new automation system. It also proposes an atomic migration strategy to
+ensure a clean and unambiguous transition.
+
+#### **2. Proposed Change**
+
+It is proposed that the new toolchain be implemented using the following structured approach:
+
+1. **Centralize Automation Logic:** A new top-level `automation/` directory will be created.
+   This directory will become the single, authoritative home for all imperative automation code
+   (Perl scripts and modules) and their corresponding tests. This cleanly separates the
+   project's declarative artifacts (in `infrastructure/` and `application/`) from the
+   imperative code that acts upon them.
+
+2. **Adopt a Test-Driven Standard:** All new Perl logic will be accompanied by a formal test
+   suite located in `automation/t/`. The project's primary test command, `meson test`, will
+   validate the correctness of the automation logic itself, enabling unit tests that can run
+   without requiring a live, deployed environment.
+
+3. **Execute an Atomic "Flag Day" Migration:** The transition from the legacy `Makefile`/`sh`
+   system will be performed in a single, comprehensive changeset. This "clean break" approach
+   avoids a confusing transitional period with two competing systems. The `Makefile` and old
+   scripts will be removed entirely, and the Meson/Perl system will be introduced as the sole,
+   official standard.
+
+#### **3. Proposed Repository Structure**
+
+The following structure is recommended to support this change. It is designed for clarity and a
+strong separation of concerns.
+
+```text
+torrust-tracker-demo/
+├── application/                # Application deployment artifacts (e.g., compose.yaml)
+├── infrastructure/             # Infrastructure-as-Code declarations (Terraform, cloud-init)
+├── docs/                       # Project documentation
+├── automation/                 # NEW: All automation logic and its tests
+│   ├── lib/                    # Reusable Perl modules (e.g., Torrust::Demo::*)
+│   ├── t/                      # Test suite for automation logic (*.t files)
+│   └── meson.build             # Defines all automation targets
+├── .gitignore
+└── meson.build                 # ROOT INTERFACE: Orchestrates all tasks
+```
+
+#### **4. Rationale for Proposed Change**
+
+This structured and test-driven approach is recommended because it allows us to build a truly
+professional-grade automation toolchain:
+
+- **Reliability Through Testing:** Implementing a test suite for our automation code is a
+  transformative step. It allows us to verify complex logic (e.g., parsing configuration,
+  generating template files) in isolation, leading to fewer bugs and faster, more confident
+  development of our tooling.
+- **Improved Maintainability:** The proposed structure creates a clear "home" for all automation
+  code. This makes the system easier for new contributors to understand and easier for
+  maintainers to extend. Separating logic into reusable Perl modules (`.pm` files) will reduce
+  code duplication and improve overall quality.
+- **Clarity of Implementation:** An atomic migration, while disruptive, provides immediate and
+  total clarity. There is no ambiguity about which system to use or how tasks should be run. All
+  documentation and workflows can be updated to reflect a single, consistent standard from day
+  one.
+
+#### **5. Scope and Relationship to Other Proposals**
+
+This document's scope is strictly limited to the **implementation strategy, repository
+structure, and testing philosophy** of the new toolchain. It defines the "how" and "where" of
+the migration.
+
+It explicitly defers the definition of specific coding conventions to the next document:
+
+- **Coding & Quality Standards (`ADR-006`):** Will define the specific rules for the Perl code
+  itself, such as mandatory pragmas (`use strict;`), security hardening (`-T`), and static
+  analysis (`Perl::Critic`) policies.
+
+#### **6. Acknowledged Trade-offs**
+
+- **One-Time Contributor Effort:** The primary trade-off is that an atomic migration requires
+  every contributor to learn and adapt to the new `meson`-based workflow simultaneously. The
+  legacy `make` commands they are familiar with will cease to exist.
+- **Mitigation Strategy:** This cost is deemed acceptable for the long-term benefit of a single,
+  superior system. The migration will be supported by a comprehensive update to all
+  documentation (`README.md`, contributing guides) and clear project-level communication to
+  prepare contributors for the change.
+
+#### **7. Next Steps**
+
+If this proposal for the implementation strategy is accepted, the maintainers will proceed with
+a final review of `ADR-006` to establish the formal coding standards before beginning the
+migration work outlined herein.

docs/adr/draft/011-perl-coding-standards.md

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+### **ADR-011: Proposal for Perl Coding and Security Standards**
+
+- **Status:** Proposed for Review
+- **Date:** 2025-07-09
+- **Proposer:** Cameron
+- **Reviewers:** [List of project maintainers/core contributors]
+- **Depends On:** [ADR-010: Proposal for a Test-Driven Implementation and Structure](./010-test-driven-implementation.md)
+
+#### **1. Context and Problem Statement**
+
+Having established the strategy (`ADR-004`) and structure (`ADR-005`) for our new Meson/Perl
+automation toolchain, it is imperative that we define a clear and enforceable set of standards
+for the code itself. Without agreed-upon conventions, the new codebase could quickly accumulate
+technical debt, becoming inconsistent, insecure, or difficult to maintain.
+
+This proposal aims to establish a baseline of quality, security, and convention for all Perl
+code within the `automation/` directory, ensuring the long-term health and clarity of our
+internal tooling.
+
+#### **2. Proposed Standards**
+
+It is proposed that the project adopt the following set of standards for all Perl code
+contributed:
+
+1. **Mandatory Pragmas for Code Safety:** It is recommended that all Perl scripts (`.pl`) and
+   modules (`.pm`) enable `use strict;`, `use warnings;`, and `use autodie;`. This combination
+   is foundational for modern, safe Perl, as it catches common errors, enforces good scoping,
+   and ensures that failed system calls result in a predictable, immediate script failure.
+
+2. **Minimum Perl Version Benchmark:** To ensure broad compatibility and stability, it is
+   proposed that the codebase target the version of Perl shipped in the **current Debian Stable
+   release**. This provides an objective benchmark that aligns development with common server
+   environments. The corresponding `use vX.XX;` pragma should be included in all Perl files to
+   enforce this minimum version.
+
+   - _As of this writing, Debian 12 ("Bookworm") ships with Perl 5.36.0. The current standard
+     would therefore be **`use v5.36;`**._
+
+3. **Static Analysis via Perl::Critic:** It is suggested that `Perl::Critic` be adopted as the
+   official linter. By integrating it into the `meson test` suite, we can provide automated
+   feedback on code style and quality for all contributions, ensuring consistency.
+
+4. **Security Hardening by Default:** It is recommended that all executable Perl scripts be run
+   with taint mode (`-T`). This is a proven security feature that prevents insecure data passed
+   from outside the program (e.g., environment variables, command-line arguments) from being
+   used in commands that interact with the shell.
+
+5. **Consistent Command-Line Interface:** To create a predictable user experience for
+   developers, it is proposed that all public-facing scripts adopt a standard CLI argument
+   style, implemented using Perl's core `Getopt::Long` module.
+
+#### **3. Rationale for Proposed Standards**
+
+Adopting this comprehensive set of standards offers clear, long-term engineering advantages:
+
+- **Reliability:** The chosen pragmas create code that is robust by default. `autodie` ensures
+  that a failed `open()` or `mkdir()` will halt execution immediately, which is critical for
+  deterministic automation.
+- **Security:** Taint mode (`-T`) provides a strong, language-level defense against a class of
+  command-injection vulnerabilities, which is a professional standard for any tool that
+  orchestrates system commands.
+- **Maintainability:** A consistent style enforced by `Perl::Critic` reduces the cognitive
+  overhead required to read, review, and maintain the codebase. Code reviews can focus on logic,
+  not formatting.
+- **Stability:** Pegging the language version to Debian Stable provides a durable and predictable
+  platform, avoiding both rapid churn from chasing the latest features and stagnation from
+  targeting old versions.
+
+#### **4. Recommended Implementation**
+
+**1. Standard Boilerplate for `.pl` and `.pm` files:**
+The following header could serve as a template for all new Perl files.
+
+```perl
+#!/usr/bin/env perl -T
+# The -T flag enables taint mode for security hardening.
+
+use strict;
+use warnings;
+# The autodie pragma automatically promotes failed system calls into exceptions.
+use autodie;
+
+# Enforce a minimum Perl version pegged to the current Debian Stable release.
+# As of Q3 2025, this is Perl 5.36 (from Debian 12 'Bookworm').
+use v5.36;
+```
+
+**2. Centralized `Perl::Critic` Configuration:**
+To manage our linting policy, a configuration file should be created at `automation/.perlcriticrc`.
+
+```ini
+# A gentle starting point that focuses on the most important issues.
+# It avoids being overly pedantic about minor style nits.
+severity = gentle
+
+# Example of disabling a specific, often-controversial policy.
+# Subroutine prototypes are used less often in modern Perl styles.
+[-Subroutines::ProhibitSubroutinePrototypes]
+```
+
+**3. Proposed Meson Integration:**
+The `meson.build` file can define clear, separate targets for testing and linting.
+
+```meson
+# In meson.build
+
+perlcritic_prog = find_program('perlcritic', required: true)
+prove_prog = find_program('prove', required: true)
+
+# Test Target 1: Code Style & Quality. Implicitly uses .perlcriticrc.
+test('Perl::Critic Linting', perlcritic_prog, args: ['automation/'])
+
+# Test Target 2: Unit Test Execution via the 'prove' TAP harness.
+test('Automation Unit Tests', prove_prog, args: ['-vr', 'automation/t/'])
+```
+
+#### **5. Acknowledged Trade-offs**
+
+- **Increased Formality:** This proposal introduces a more formal development process.
+  Contributors will need to adhere to these standards, which is more restrictive than writing
+  simple shell scripts. This is presented as a beneficial trade-off for the gains in long-term
+  quality and security.
+- **Exclusion of Newer Language Features:** The project would intentionally be unable to use
+  Perl features newer than what is available in the benchmarked Debian Stable release. This is a
+  deliberate choice prioritizing stability and compatibility.
+
+#### **6. Next Steps**
+
+If this proposal is accepted, it will serve as the official quality standard for all code
+developed during the migration outlined in `ADR-005`. All new Perl contributions will be
+expected to adhere to these rules, which will be enforced automatically by the CI pipeline.