Write a REST API in Any Language

Build a REST API for [WHAT IT DOES] using [LANGUAGE / FRAMEWORK, e.g. Python + FastAPI / Node.js + Express / Go + Gin].

Include:

1) All necessary endpoints with HTTP methods (GET, POST, PUT, DELETE as needed)
2) Request and response schema with example JSON for each endpoint
3) Basic input validation and error handling with appropriate HTTP status codes
4) A simple in-memory data store or database connection to [DATABASE, e.g. PostgreSQL / SQLite / MongoDB]
5) Comments explaining key sections
6) Instructions to run the server locally. Keep the code production-ready and follow REST best practices