added Creating Groups to frontend and saving them in Database. Also prepared some Methods for Snapshot db

src/main/java/mops/gruppen2/domain/event/DeleteUserEvent.java

@@ -6,11 +6,9 @@ import lombok.*;
  * Entfernt ein einzelnes Mitglied einer Gruppe.
  */
 @Getter
-@AllArgsConstructor
-@NoArgsConstructor
 public class DeleteUserEvent extends Event {
 
-    public DeleteUserEvent(long event_id, long group_id, String user_id) {
+    public DeleteUserEvent(Long event_id, Long group_id, String user_id) {
         super(event_id, group_id, user_id);
     }
 }