REST API Endpoint Generator

Design and implement a REST API endpoint for [ENDPOINT PURPOSE — e.g. 'user authentication', 'product search', 'order creation']. Stack: [LANGUAGE/FRAMEWORK — Node.js/Express, Python/FastAPI, etc.]. Include: (1) the route definition with HTTP method and path, (2) request validation (required fields, types, constraints), (3) business logic with inline comments, (4) success response with example JSON (200/201), (5) error responses for: 400 bad request, 401 unauthorized, 404 not found, 500 server error, (6) one middleware function for authentication/logging if relevant. Follow RESTful conventions. Add JSDoc or docstring comments.