sanjaybr5799/ChildGuard ? reverse-engineered prompt

Build me a simple course registration service with REST APIs.

I want to be able to create, view, update, and delete course registrations, and store everything in MongoDB. Please make it easy to run locally with a single start command after setting up a .env file for the port and database connection.

Include a clean data model for registrations, and make sure the API follows a sensible structure with routes, controllers, models, and services if needed. It should return clear success and error responses, and handle bad input nicely.

If there’s an OpenAPI spec or API collection that would help, add that too so I can test the endpoints easily. Use the existing README as the main guide, and if anything is unclear, look up the current docs online and fill in the gaps in a practical way.