title: How to replace Symfony2's CsrfProvider with another service?
body: <p>Symfony2's default SessionCsrfProvider can be replaced with another service that implements <a href="http://api.symfony.com/2.1/Symfony/Component/Form/Extension/Csrf/CsrfProvider/CsrfProviderInterface.html" rel="nofollow">CsrfProviderInterface</a>. However, the documentation does not tell where to define the replacing service id.</p>
  
  <p>The <a href="http://symfony.com/doc/current/reference/configuration/framework.html#full-default-configuration" rel="nofollow">default framework configuration</a> allows only to set field_name and enabled/disabled flag. There is no similar configuration option as "storage_id" in sessions.</p>
  
  <p>So, how to replace the default CSRF Provider?</p>