NewUserHandler creates a new Handler instance with the provided userService.

NewUserRepository creates a new instance of userRepositoryImpl with the provided database connection.

NewUserService creates a new instance of userServiceImpl with the provided Repository.

Router sets up the routes for the user-related API endpoints.

Handler struct represents the HTTP handler for user-related operations.

Repository defines the interface for user-related data operations.

Service defines the methods that our User Service should implement.