Merge branch '5.3' into 5.4

* 5.3:
  [Tests] Remove some unused fixtures
  added missing translations for portuguese [#43726]
  [HttpClient][Mime] Add correct IDN flags for IDNA2008 compliance
  properly parse quoted strings tagged with !!str
  do not merge label classes into expanded choice labels
  [Serializer] PropertyNormalizer - return unique (i.e. filter duplicate ) attributes in extractAttributes function

Author: derrabus

Tests/DependencyInjection/SecurityExtensionTest.php

@@ -36,7 +36,6 @@
 use Symfony\Component\Security\Core\User\UserCheckerInterface;
 use Symfony\Component\Security\Core\User\UserInterface;
 use Symfony\Component\Security\Core\User\UserProviderInterface;
-use Symfony\Component\Security\Guard\AuthenticatorInterface as GuardAuthenticatorInterface;
 use Symfony\Component\Security\Guard\Token\GuardTokenInterface;
 use Symfony\Component\Security\Http\Authenticator\AuthenticatorInterface;
 use Symfony\Component\Security\Http\Authenticator\HttpBasicAuthenticator;
@@ -894,45 +893,6 @@ public function createToken(Passport $passport, string $firewallName): TokenInte
     }
 }
 
-class NullAuthenticator implements GuardAuthenticatorInterface
-{
-    public function start(Request $request, AuthenticationException $authException = null): Response
-    {
-    }
-
-    public function supports(Request $request): bool
-    {
-    }
-
-    public function getCredentials(Request $request)
-    {
-    }
-
-    public function getUser($credentials, UserProviderInterface $userProvider): ?UserInterface
-    {
-    }
-
-    public function checkCredentials($credentials, UserInterface $user): bool
-    {
-    }
-
-    public function createAuthenticatedToken(UserInterface $user, string $providerKey): GuardTokenInterface
-    {
-    }
-
-    public function onAuthenticationFailure(Request $request, AuthenticationException $exception): ?Response
-    {
-    }
-
-    public function onAuthenticationSuccess(Request $request, TokenInterface $token, string $providerKey): ?Response
-    {
-    }
-
-    public function supportsRememberMe(): bool
-    {
-    }
-}
-
 class TestUserChecker implements UserCheckerInterface
 {
     public function checkPreAuth(UserInterface $user)