minor #949 Redirect to the right page after changing the locale in the login page (javiereguiluz)

This PR was squashed before being merged into the master branch (closes #949).

Discussion
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Redirect to the right page after changing the locale in the login page

This fixes the problem reported in symfony/symfony-docs#10864

I don't think this is a Symfony bug or a Demo app bug ... I think it's an edge case for the reasons explained in the code ... and that's why I propose this solution.

Commits
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e493643 Redirect to the right page after changing the locale in the login page

Author: javiereguiluz

src/Controller/SecurityController.php

@@ -12,9 +12,11 @@
 namespace App\Controller;
 
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Routing\Annotation\Route;
 use Symfony\Component\Security\Http\Authentication\AuthenticationUtils;
+use Symfony\Component\Security\Http\Util\TargetPathTrait;
 
 /**
  * Controller used to manage the application security.
@@ -25,11 +27,19 @@
  */
 class SecurityController extends AbstractController
 {
+    use TargetPathTrait;
+
     /**
      * @Route("/login", name="security_login")
      */
-    public function login(AuthenticationUtils $helper): Response
+    public function login(Request $request, AuthenticationUtils $helper): Response
     {
+        // this statement solves an edge-case: if you change the locale in the login
+        // page, after a successful login you are redirected to a page in the previous
+        // locale. This code regenerates the referrer URL whenever the login page is
+        // browsed, to ensure that its locale is always the current one.
+        $this->saveTargetPath($request->getSession(), 'main', $this->generateUrl('admin_index'));
+
         return $this->render('security/login.html.twig', [
             // last username entered by the user (if any)
             'last_username' => $helper->getLastUsername(),