minor #5993 [Cookbook] [Security] Use UserLoaderInterface instead of UserProviderInterface (ogizanagi)

This PR was merged into the 2.8 branch.

Discussion
----------

[Cookbook] [Security] Use UserLoaderInterface instead of UserProviderInterface

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.8+
| Fixed tickets | #5968

Commits
-------

79ec09a [Cookbook] [Security] Use UserLoaderInterface instead of UserProviderInterface

Author: xabbuh

cookbook/security/entity_provider.rst

@@ -424,20 +424,18 @@ both are unique in the database. Unfortunately, the native entity provider
 is only able to handle querying via a single property on the user.
 
 To do this, make your ``UserRepository`` implement a special
-:class:`Symfony\\Component\\Security\\Core\\User\\UserProviderInterface`. This
-interface requires three methods: ``loadUserByUsername($username)``,
-``refreshUser(UserInterface $user)``, and ``supportsClass($class)``::
+:class:`Symfony\\Bridge\\Doctrine\\Security\\User\\UserLoaderInterface`. This
+interface only requires one method: ``loadUserByUsername($username)``::
 
     // src/AppBundle/Entity/UserRepository.php
     namespace AppBundle\Entity;
 
+    use Symfony\Bridge\Doctrine\Security\User\UserLoaderInterface;
     use Symfony\Component\Security\Core\User\UserInterface;
-    use Symfony\Component\Security\Core\User\UserProviderInterface;
     use Symfony\Component\Security\Core\Exception\UsernameNotFoundException;
-    use Symfony\Component\Security\Core\Exception\UnsupportedUserException;
     use Doctrine\ORM\EntityRepository;
 
-    class UserRepository extends EntityRepository implements UserProviderInterface
+    class UserRepository extends EntityRepository implements UserLoaderInterface
     {
         public function loadUserByUsername($username)
         {
@@ -458,30 +456,12 @@ interface requires three methods: ``loadUserByUsername($username)``,
 
             return $user;
         }
-
-        public function refreshUser(UserInterface $user)
-        {
-            $class = get_class($user);
-            if (!$this->supportsClass($class)) {
-                throw new UnsupportedUserException(
-                    sprintf(
-                        'Instances of "%s" are not supported.',
-                        $class
-                    )
-                );
-            }
-
-            return $this->find($user->getId());
-        }
-
-        public function supportsClass($class)
-        {
-            return $this->getEntityName() === $class
-                || is_subclass_of($class, $this->getEntityName());
-        }
     }
 
-For more details on these methods, see :class:`Symfony\\Component\\Security\\Core\\User\\UserProviderInterface`.
+.. versionadded:: 2.8
+    The :class:`Symfony\\Bridge\\Doctrine\\Security\\User\\UserLoaderInterface`
+    interface was introduced in 2.8. Prior to Symfony 2.8, you had to implement
+    ``Symfony\Component\Security\Core\User\UserProviderInterface``.
 
 .. tip::