fix(google-ads): fix campaign and keyword metrics validation errors and ROAS calculations

[AlexanderHeffernan]

Description

• Purpose: Fix data format validation errors and incorrect ROAS calculations in Google Ads campaign and keyword metrics retrieval.
• Approach: Wrap API responses in the expected schema format and correct the default value for missing cost data to prevent calculation errors.

Type of change

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

Updates

👉 Wrapped retrieve_campaign_metrics and retrieve_keyword_metrics responses in {"results": ...} object to match expected output schema and fix production ValidationError
👉 Changed default cost_micros value from 1 to 0 when missing to prevent incorrect Return On Ad Spend (ROAS) calculations
👉 Applied consistent response format across both campaign and keyword metrics endpoints

Screenshots

N/A

Test plan

1. Test retrieve_campaign_metrics action with valid customer ID and verify response format matches {"results": [...]} schema
2. Test retrieve_keyword_metrics action with valid parameters and verify response format is correct
3. Verify ROAS calculations are accurate when cost_micros is missing (should be 0, not inflated by default value of 1)
4. Confirm no ValidationErrors occur in production when these actions are executed

Author(s) to check

• Project and all contained modules builds successfully
• Self-/dev-tested
• Unit/UI/Automation/Integration tests provided where applicable
• Code is written to standards
• Appropriate documentation written (code comments, internal docs)