[CORE][Form] Add facilities for automattically adding a _next field to all forms, which can be customized by the in Form::create and defaults to the current URL. Usage of RedirectedException should mostly be replaced with Form::forceRedirect

src/Core/Form.php

@@ -33,8 +33,10 @@ declare(strict_types = 1);
 namespace App\Core;
 
 use App\Core\DB\DB;
+use function App\Core\I18n\_m;
 use App\Core\Router\Router;
 use App\Util\Common;
+use App\Util\Exception\ClientException;
 use App\Util\Exception\RedirectException;
 use App\Util\Exception\ServerException;
 use App\Util\Formatting;
@@ -45,6 +47,7 @@ use Symfony\Component\Form\FormFactoryInterface;
 use Symfony\Component\Form\FormInterface as SymfFormInterface;
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\Routing\Exception\ResourceNotFoundException;
 
 /**
  * This class converts our own form representation to Symfony's
@@ -224,11 +227,10 @@ abstract class Form
                 $next     = mb_substr($next, 0, $pos);
             }
             Router::match($next);
-            $next = $next . ($fragment ?? '');
             return new RedirectResponse(url: $next . ($fragment ?? ''));
         } catch (ResourceNotFoundException $e) {
             $user    = Common::user();
-            $user_id = \is_null($user) ? $user->getId() : '(not logged in)';
+            $user_id = !\is_null($user) ? $user->getId() : '(not logged in)';
             Log::warning("Suspicious activity: User with ID {$user_id} submitted a form where the `_next` parameter is not a valid local URL ({$next})");
             throw new ClientException(_m('Invalid form submission'), $e);
         }