[CORE][EVENTS] Bring existing Events and Boostrapper back

- Adapt the existing event system to rely on Symfony's event dispatcher

src/Controller/NetworkPublic.php

@@ -5,12 +5,13 @@ namespace App\Controller;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 
-use App;
+use App\Util\GSEvent;
 
 class NetworkPublic extends AbstractController
 {
     public function __invoke()
     {
+        GSEvent::handle('test', ['foobar']);
         return $this->render('network/public.html.twig', []);
     }
 }