AP-2520 Add Iceberg table support to target-snowflake

[louis-pie]

Context

Add minimal support for PipelineWise to be able to write to an Iceberg table already defined in Snowflake.
PipelineWise will not create the Iceberg table, but if the table is already there it will not attempt to convert it back to a native table.

Types of changes

What types of changes does your code introduce to PipelineWise?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue) [optional]
• New feature (non-breaking change which adds functionality) [optional]
• Breaking change (fix or feature that would cause existing functionality to not work as expected) [optional]
• Documentation Update (if none of the other choices apply) [optional]

Checklist

• I have read the CONTRIBUTING doc
• Description above provides context of the change
• I have added tests that prove my fix is effective or that my feature works
• Unit tests for changes (not needed for documentation changes)
• CI checks pass with my changes
• Branch name starts with AP-NNN (if applicable. AP-NNN = JIRA ID)
• Relevant documentation is updated including usage instructions

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[Copilot]

Pull Request Overview

This PR adds minimal support for Iceberg tables in Snowflake to PipelineWise. The implementation allows PipelineWise to work with pre-existing Iceberg tables without attempting to convert them back to native Snowflake tables. Key changes include type mapping adjustments (using string instead of variant for object/array types), detection logic to identify Iceberg tables, and safeguards to prevent automatic schema alterations on Iceberg tables.

Key Changes

• Added is_iceberg_table parameter to column_type() function to handle Iceberg-specific type mappings
• Implemented iceberg_get_tables() method to query Snowflake metadata for Iceberg tables
• Modified update_columns() and sync_table() to detect Iceberg tables and prevent automatic alterations, requiring manual column changes instead

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 9 comments.

File	Description
singer-connectors/target-snowflake/target_snowflake/db_sync.py	Core implementation: added Iceberg table detection, type mapping for Iceberg compatibility, and logic to prevent automatic schema changes on Iceberg tables
singer-connectors/target-snowflake/target_snowflake/init.py	Updated log message for clarity ("PipelineWise table cache")
dev-project/docker-compose.yml	Adjusted Snowflake PEM file mount path from /opt/pipelinewise/.ssh/ to /root/.ssh/
.gitignore	Added dev-project/snowflake.pem to ignored files for security

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