Merge Fixes + Code Style

...main/java/com/mif13/authServer/AuthServerApplication.java

...java/com/mif13/authServer/controllers/UserOperations.java

.../com/mif13/authServer/controllers/UserRestController.java

auth-server/src/main/java/com/mif13/authServer/dao/Dao.java

.../mif13/authServer/exception/InvalidPasswordException.java

.../mif13/authServer/exception/InvalidUsernameException.java

...com/mif13/authServer/exception/UserCreationException.java

...server/src/main/java/com/mif13/authServer/model/User.java

.../src/main/java/com/mif13/authServer/utils/CorsConfig.java

...r/src/main/java/com/mif13/authServer/utils/JwtHelper.java