[Integration]: Google Analytics - Website Traffic & Marketing Performance #3727

[Ttian18]

Description

Add Google Analytics 4 (GA4) integration as a new MCP tool package,
providing read-only access to the GA4 Data API v1.

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Related Issues

Closes #3727

Changes Made

• Credential spec (credentials/google_analytics.py): service account key path via GOOGLE_APPLICATION_CREDENTIALS
• Tool package (tools/google_analytics_tool/): 4 MCP tools
  • ga_run_report — custom report with flexible dimensions, metrics, date ranges
  • ga_get_realtime — real-time active users and current pages
  • ga_get_top_pages — top pages by views and engagement
  • ga_get_traffic_sources — traffic breakdown by source/medium
• Registration in credentials/__init__.py and tools/__init__.py
• README with setup guide, argument tables, and examples
• 43 unit tests covering client formatting, credential retrieval, input validation, API calls, error handling, and tool registration

Testing

• 43 GA-specific tests pass
• Full suite: 770 passed, 30 skipped, 0 failures
• Lint and format checks clean

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes