agesart-gif/saas-backend — reverse-engineered prompt

Build me a simple SaaS backend in JavaScript that can run locally with npm start and connect to a database using an environment variable. I need basic user management endpoints so I can create users, list users, get one user, update a user, and delete a user.

Also set it up so it’s ready for future SaaS features like an AI chatbot, WhatsApp messaging, and social media posting. The actual integrations can be simple starter examples or clean service files that call outside APIs when keys are added. Use JWT secret configuration so authentication can be added or protected routes can work.

Please include a clear .env example, database migrations if needed, and API documentation with Swagger so I can test the endpoints easily. Make sure the project is easy to deploy on a Node server later, with sensible error handling and a straightforward README explaining setup, configuration, and how to run it.