core: allow filtering users by the groups they are in

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

internal/outpost/ldap/instance_search_group.go

@@ -42,6 +42,7 @@ func parseFilterForGroupSingle(req api.ApiCoreGroupsListRequest, f *ber.Packet)
 		case "cn":
 			return req.Name(vv)
 		case "member":
+		case "memberOf":
 			userDN, err := goldap.ParseDN(vv)
 			if err != nil {
 				return req