Merge refactor into error-handling + fix merge errors

Co-authored-by: [Mahgs] <maxoerter@gmx.de>
Co-authored-by: Christoph <tobi@urpost.de>

src/main/java/mops/gruppen2/domain/exception/UserNotFoundException.java

@@ -1,8 +1,10 @@
 package mops.gruppen2.domain.exception;
 
+import org.springframework.http.HttpStatus;
+
 public class UserNotFoundException extends EventException {
 
-    public UserNotFoundException(String msg) {
-        super(msg);
+    public UserNotFoundException(String info) {
+        super(HttpStatus.NOT_FOUND, "Der User wurde nicht gefunden.", info);
     }
 }