CU Auth external dependency

[woodseowl]

Factors CUAuth out as a separate package through cornell-custom-dev/laravel-cu-auth.

• composer requires cornell-custom-dev/laravel-cu-auth (which provides PHP SAML library)
• removes the CUAuth directory and installer test
• expands the "starterkit:install" command (with test coverage) to install cu-auth configs

[Copilot]

Pull Request Overview

This PR extracts the CUAuth functionality into a separate external package (cornell-custom-dev/laravel-cu-auth), removing the embedded implementation and updating the starter kit to depend on and configure the external package instead.

• Removes all CUAuth source code and tests from the starter kit package
• Adds dependency on cornell-custom-dev/laravel-cu-auth package
• Expands the install command to support configuring the external CUAuth package with SAML certificates

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
composer.json	Adds dependency on cornell-custom-dev/laravel-cu-auth package and removes internal CUAuth service provider
src/StarterKitServiceProvider.php	Adds install options for PHP SAML toolkit configuration and certificate generation
tests/Feature/InstallStarterKitTest.php	Updates tests to cover new install options and removes obsolete CUAuth installer test
src/CUAuth/*	Removes all CUAuth source files (middleware, controllers, events, listeners, data objects, service provider, routes, config, documentation)
README.md	Updates CUAuth description and PHP version reference

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