Merge branch '6.3' into 6.4

* 6.3:
  [TwigBridge] Change return type of Symfony\Bridge\Twig\AppVariable::getSession()
  [mailer] reset $code variable each iteration for prevent wrong codes to be used
  bug [mailer] fix EsmtpTransport variable $code definition
  UrlHelper: minor code style fix
  [Serializer] Looking for DiscriminatorMap on interfaces when the current object also extends from a class
  [DoctrineBridge][Security] Rename loadUserByUsername tests to loadUserByIdentifier

Author: fabpot

Tests/User/ChainUserProviderTest.php

@@ -23,7 +23,7 @@
 
 class ChainUserProviderTest extends TestCase
 {
-    public function testLoadUserByUsername()
+    public function testLoadUserByIdentifier()
     {
         $provider1 = $this->createMock(InMemoryUserProvider::class);
         $provider1
@@ -45,7 +45,7 @@ public function testLoadUserByUsername()
         $this->assertSame($account, $provider->loadUserByIdentifier('foo'));
     }
 
-    public function testLoadUserByUsernameThrowsUserNotFoundException()
+    public function testLoadUserByIdentifierThrowsUserNotFoundException()
     {
         $this->expectException(UserNotFoundException::class);
         $provider1 = $this->createMock(InMemoryUserProvider::class);

Tests/User/InMemoryUserProviderTest.php

@@ -68,7 +68,7 @@ public function testCreateUserAlreadyExist()
         $provider->createUser(new InMemoryUser('fabien', 'foo'));
     }
 
-    public function testLoadUserByUsernameDoesNotExist()
+    public function testLoadUserByIdentifierDoesNotExist()
     {
         $this->expectException(UserNotFoundException::class);
         $provider = new InMemoryUserProvider();