change AddUserEvent and DeleteUserEvent

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

@@ -1,15 +1,21 @@
 package mops.gruppen2.domain.event;
 
 import lombok.*;
+import mops.gruppen2.domain.Group;
+import mops.gruppen2.domain.User;
 
 /**
  * Entfernt ein einzelnes Mitglied einer Gruppe.
  */
 @Getter
 public class DeleteUserEvent extends Event { 
-    public DeleteUserEvent(Long event_id, Long group_id, String user_id) {
-        super(event_id, group_id, user_id);
+    public DeleteUserEvent(Long group_id, String user_id) {
+        super(group_id, user_id);
     }
 
     public DeleteUserEvent() {}
+
+    public void apply(Group group, User user) {
+        group.getMembers().remove(user);
+    }
 }