add record route for notify

kamailio/default.cfg

@@ -468,6 +468,10 @@ route[HANDLE_IN_DIALOG_REQUESTS]
         route(RELAY);
     } else if (t_check_trans()) {
         xlog("L_INFO", "$ci|log|allow message for a known transaction\n");
+        if ( is_method("NOTIFY") ) {
+             # Add Record-Route for in-dialog NOTIFY as per RFC 6665.
+             record_route();
+        }
         route(RELAY);
     } else {
         xlog("L_INFO", "$ci|log|message had a to-tag but can't be loose routed\n");