add customization points

kamailio/default.cfg

@@ -324,6 +324,8 @@ route
 
     route(HANDLE_OPTIONS);
 
+    route_if_exists("CUSTOM_START_ROUTES");
+
     route(HANDLE_NOTIFY);
 
     #!ifdef AUTHORIZATION_ROLE
@@ -919,4 +921,6 @@ event_route[tm:local-request]
 }
 #!endif
 
+#!import_file "custom-routes.cfg"
+
 # vim: tabstop=4 softtabstop=4 shiftwidth=4 expandtab