router.addRoutes() is deprecated and has been removed in Vue Router 4. Use router.addRoute() instead.

This message is a deprecation warning that informs developers that the method `addRoutes()` in Vue Router is no longer available in version 4 and has been replaced with `addRoute()`. Therefore, to add routes to a Vue Router instance in version 4, developers should use `addRoute()` instead of `addRoutes()`. This change was made to simplify the API for adding routes and to make it more intuitive. Developers should update their code accordingly to avoid any issues when upgrading to Vue Router 4.