add property to route service provider

app/Providers/RouteServiceProvider.php

@@ -19,6 +19,15 @@ class RouteServiceProvider extends ServiceProvider
      */
     public const HOME = '/home';
 
+    /**
+     * If specified, this namespace is automatically applied to your controller routes.
+     *
+     * In addition, it is set as the URL generator's root namespace.
+     *
+     * @var string
+     */
+    protected $namespace = null;
+
     /**
      * Define your route model bindings, pattern filters, etc.
      *