merged branch elnur/chain-user-provider-getter (PR #7077)

This PR was merged into the master branch.

Discussion
----------

[2.3] [Security] Add a getter for providers to the ChainUserProvider class

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes

I've got a use case where I need to check if any of the chained user providers implement a particular interface. This getter would really help with that.

Commits
-------

0a82d73 Add a getter for providers to the ChainUserProvider class

src/Symfony/Component/Security/Core/User/ChainUserProvider.php

@@ -31,6 +31,14 @@ public function __construct(array $providers)
         $this->providers = $providers;
     }
 
+    /**
+     * @return array
+     */
+    public function getProviders()
+    {
+        return $this->providers;
+    }
+
     /**
      * {@inheritDoc}
      */