feature #11306 [DX] New service to simplify password encoding (aferrandini)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[DX] New service to simplify password encoding

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11299
| License       | MIT
| Doc PR | https://github.com/symfony/symfony-docs/pull/3995

This new service siplifies the way to encode a password. Just get the `security.password_encoder` service and encode the `User` password.

```php
$encoded = $this->container->get('security.password_encoder')
    ->encodePassword($user, $plainPassword);

$user->setPassword($encoded);
```

Commits
-------

7bc190a New service to simplify password encoding

2 files changed, 96 insertions, 0 deletions

diff --git a/Core/Encoder/UserPasswordEncoder.php b/Core/Encoder/UserPasswordEncoder.php
new file mode 100644
index 0000000..13ee835
--- /dev/null
+++ b/Core/Encoder/UserPasswordEncoder.php
@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Security\Core\Encoder;
+
+use Symfony\Component\Security\Core\User\UserInterface;
+
+/**
+ * A generic password encoder
+ *
+ * @author Ariel Ferrandini <arielferrandini@gmail.com>
+ */
+class UserPasswordEncoder implements UserPasswordEncoderInterface
+{
+    /**
+     * @var EncoderFactoryInterface
+     */
+    private $encoderFactory;
+
+    /**
+     * @param EncoderFactoryInterface $encoderFactory The encoder factory
+     */
+    public function __construct(EncoderFactoryInterface $encoderFactory)
+    {
+        $this->encoderFactory = $encoderFactory;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function encodePassword(UserInterface $user, $plainPassword)
+    {
+        $encoder = $this->encoderFactory->getEncoder($user);
+
+        return $encoder->encodePassword($plainPassword, $user->getSalt());
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isPasswordValid(UserInterface $user, $raw)
+    {
+        $encoder = $this->encoderFactory->getEncoder($user);
+
+        return $encoder->isPasswordValid($user->getPassword(), $raw, $user->getSalt());
+    }
+}
diff --git a/Core/Encoder/UserPasswordEncoderInterface.php b/Core/Encoder/UserPasswordEncoderInterface.php
new file mode 100644
index 0000000..39e906a
--- /dev/null
+++ b/Core/Encoder/UserPasswordEncoderInterface.php
@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Security\Core\Encoder;
+
+use Symfony\Component\Security\Core\User\UserInterface;
+
+/**
+ * UserPasswordEncoderInterface is the interface for the password encoder service.
+ *
+ * @author Ariel Ferrandini <arielferrandini@gmail.com>
+ */
+interface UserPasswordEncoderInterface
+{
+    /**
+     *
+     * Encodes the plain password.
+     *
+     * @param UserInterface $user          The user
+     * @param string        $plainPassword The password to encode
+     *
+     * @return string The encoded password
+     */
+    public function encodePassword(UserInterface $user, $plainPassword);
+
+    /**
+     * @param UserInterface $user The user
+     * @param string        $raw  A raw password
+     *
+     * @return bool true if the password is valid, false otherwise
+     */
+    public function isPasswordValid(UserInterface $user, $raw);
+}