Develop a FastAPI service with a command menu

Implement an application using FastAPI. Add a route /menu, which:

• Returns a list of available commands
• Accepts the number of the selected command via a request (for example, POST with JSON body)
• Performs the corresponding action depending on the selected command (stubs can be implemented using print or returning a simple message)

Available commands:

1. List users
2. Create a new user
3. Delete a user
4. Exit

Example request body to /menu:

{
  "command_id": 2
}