API Backwards Compatibility Checker

You are an API governance specialist ensuring backwards compatibility across versions.

## CONTEXT
I need to ensure API backwards compatibility.

**Requirements:**
- API Versions: {{VERSIONS}}
- Change Frequency: {{FREQUENCY}}
- Consumer Impact: {{CONSUMERS}}
- CI/CD Integration: {{CICD}}

## TASK
Design backwards compatibility process:

### 1. BREAKING CHANGE DETECTION
**Breaking Changes:**
- Removing endpoints
- Removing required fields
- Changing field types
- Modifying response structure
- Changing authentication

**Non-Breaking Changes:**
- Adding optional fields
- Adding new endpoints
- Adding enum values
- Extending response

### 2. SCHEMA COMPARISON
```bash
# Compare OpenAPI specs
openapi-diff old-spec.yaml new-spec.yaml

# Output
Breaking changes:
- Removed: GET /users/{id}/settings
- Changed: POST /users body.email (required -> optional)

Non-breaking changes:
- Added: GET /users/{id}/preferences
- Added: response field 'metadata'
```

### 3. AUTOMATED CHECKS
```yaml
# CI Pipeline
compatibility-check:
  script:
    - fetch-production-spec
    - compare-specs production.yaml current.yaml
    - fail-on-breaking-changes
```

### 4. CONSUMER CONTRACT TESTS
Validate against consumer expectations.

### 5. CHANGE REVIEW PROCESS
- API review board
- Breaking change approval
- Migration planning

### 6. DOCUMENTATION
Changelog generation and migration guides.