renforcement de sécurité

...gestionstagesbackend/GestionStagesBackendApplication.java

...m/example/gestionstagesbackend/config/SecurityConfig.java

...ple/gestionstagesbackend/controllers/AdminController.java

...mple/gestionstagesbackend/controllers/AuthController.java

...gestionstagesbackend/controllers/CandidacyController.java

...estionstagesbackend/controllers/EnterpriseController.java

...ple/gestionstagesbackend/controllers/StageController.java

...e/gestionstagesbackend/controllers/StudentController.java

...onstagesbackend/controllers/UnivSupervisorController.java

...ain/java/com/example/gestionstagesbackend/model/User.java

...ple/gestionstagesbackend/repositories/UserRepository.java

...om/example/gestionstagesbackend/services/UserService.java