Ensure routes are only populated after extensions have registered listeners

Because extensions can have dependencies injected, a RouteCollection could potentially be instantiated, and thus the ConfigureRoutes event would be called before extensions have had a chance to subscribe to it. Instead, we instantiate the RouteCollection on demand, but only populate it when the application boots.

src/Admin/AdminServiceProvider.php

@@ -33,7 +33,7 @@ class AdminServiceProvider extends AbstractServiceProvider
         });
 
         $this->app->singleton('flarum.admin.routes', function () {
-            return $this->getRoutes();
+            return new RouteCollection;
         });
     }
 
@@ -42,6 +42,8 @@ class AdminServiceProvider extends AbstractServiceProvider
      */
     public function boot()
     {
+        $this->populateRoutes($this->app->make('flarum.admin.routes'));
+
         $this->loadViewsFrom(__DIR__.'/../../views', 'flarum.admin');
 
         $this->flushAssetsWhenThemeChanged();
@@ -50,14 +52,12 @@ class AdminServiceProvider extends AbstractServiceProvider
     }
 
     /**
-     * Register the admin client routes.
+     * Populate the forum client routes.
      *
-     * @return RouteCollection
+     * @param RouteCollection $routes
      */
-    protected function getRoutes()
+    protected function populateRoutes(RouteCollection $routes)
     {
-        $routes = new RouteCollection;
-
         $toController = $this->getHandlerGenerator($this->app);
 
         $routes->get(
@@ -65,8 +65,6 @@ class AdminServiceProvider extends AbstractServiceProvider
             'index',
             $toController('Flarum\Admin\Controller\ClientController')
         );
-
-        return $routes;
     }
 
     protected function flushAssetsWhenThemeChanged()