Create API Fixture Validator

[Mosas2000]

Description

Validate that fixture payloads used in tests still match the current API shapes.

Requirements and context

• Fixture drift detection
• Schema matching
• Readable diffs
• CI support
• Coverage of key payloads

Suggested execution

Fork the repo and create a branch

git checkout -b feature/testing-api-fixture-validator

Implement changes

• Create fixture validator
• Run checks in CI
• Flag stale fixtures
• Document update workflow

Example commit message

test: create api fixture validator

Guidelines

• Assignment required before starting
• PR must include a closing reference to this issue
• Timeframe: 72 hours