add Event related stuff and Group example

src/main/java/mops/gruppen2/Events/CreateGroupEvent.java

@@ -0,0 +1,17 @@
+package mops.gruppen2.Events;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.Getter;
+
+@Getter
+public class CreateGroupEvent extends Event{
+	String titel;
+	String beschreibung;
+
+	public CreateGroupEvent(Long id, Long gruppe_id, Long user_id, String titel,String beschreibung) {
+		super(id, gruppe_id, user_id);
+		this.titel = titel;
+		this.beschreibung = beschreibung;
+	}
+}