Add security on endpoints and handle 403 responses.

sportshub-exposition/src/main/java/org/sportshub/exposition/user/UserController.java

@@ -1,12 +1,10 @@
 package org.sportshub.exposition.user;
 
 import java.util.List;
-import java.util.Optional;
 
 import org.sportshub.application.user.UserUseCases;
 import org.sportshub.domain.user.model.User;
 import org.sportshub.exposition.user.model.LoginRequest;
-import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestBody;