Implement User CRUD Operations

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1. Create UserController:

   • Define a UserController class with the following endpoints:
     • POST /api/users → Create a new user.
     • GET /api/users/{id} → Get user details by ID.
     • PUT /api/users/{id} → Update user information.
     • DELETE /api/users/{id} → Delete a user.
     • GET /api/users → List all users (admin only).

2. UserService:

   • Implement business logic in the UserService class.
   • Handle user creation, fetching, updating, and deletion logic.
     • Use UserRepository to interact with the database.
     • Make sure to handle scenarios like when a user doesn’t exist (404) or when data is invalid (400).

3. UserRepository:

   • Include queries for fetching users by ID, updating user info, deleting users, and listing all users.
     • Use findById, save, deleteById, and custom queries where necessary.

4. Test CRUD Operations in Postman:

   • Test the CRUD endpoints by sending requests to the server and checking the responses.
   • For each endpoint, check for correct status codes (e.g., 201 for creation, 200 for successful update, 404 for non-existing user).
   • Verify that user data is stored in the database after successful creation and update.