Data Validation Schema Generator

Generate {{schema_format}} validation schemas for this API contract:

{{api_contract}}

Requirements:
- Error format: {{error_format}}
- Localization: {{localization}}
- Custom validators: {{custom_rules}}
- Framework: {{framework}}

Provide:
1. Complete schema definitions with descriptions
2. Composite validation rules (cross-field)
3. Error message templates ({{error_locales}})
4. Runtime codec (serialization/deserialization)
5. Test cases (valid, invalid, edge cases)