API Request Validation Framework

Build a request validation framework for:

Framework: [Express/FastAPI/Django/etc.]
Language: [TypeScript/Python/Java]
Validation Library: [Zod/Joi/Pydantic/etc.]

Validation Needs:
- Request body validation
- Query parameter validation
- Path parameter validation
- Custom business rules

Please provide:
1. Validation schema definitions
2. Middleware/decorator implementation
3. Custom validator creation
4. Error message formatting
5. Sanitization strategies
6. OpenAPI/Swagger integration