OZG-2652 cleanup Exception/Log handling

src/main/java/de/itvsh/kop/user/UserService.java

...itvsh/kop/user/common/errorhandling/ExceptionHandler.java

...n/java/de/itvsh/kop/user/keycloak/KeycloakApiService.java

src/main/java/de/itvsh/kop/user/sync/LockService.java

src/main/java/de/itvsh/kop/user/sync/SyncService.java

src/test/java/de/itvsh/kop/user/UserRepositoryTest.java

...h/kop/user/common/errorhandling/ExceptionHandlerTest.java