OO-3541: persist the last modification date a membership

src/main/java/org/olat/basesecurity/model/GroupMembershipImpl.java

@@ -85,7 +85,7 @@ public class GroupMembershipImpl implements GroupMembership, ModifiedInfo, Persi
 	private Date creationDate;
 	
 	@Temporal(TemporalType.TIMESTAMP)
-	@Column(name="lastmodified", nullable=false, insertable=true, updatable=false)
+	@Column(name="lastmodified", nullable=false, insertable=true, updatable=true)
 	private Date lastModified;
 	
 	@Column(name="g_role", nullable=false, insertable=true, updatable=false)

src/main/java/org/olat/group/manager/BusinessGroupRelationDAO.java

@@ -295,6 +295,7 @@ public class BusinessGroupRelationDAO {
 				.getResultList();
 		for(GroupMembershipImpl membership:memberships) {
 			membership.setLastModified(new Date());
+			dbInstance.getCurrentEntityManager().merge(membership);
 		}
 	}