title: symfony 3 unrecognized option in services
body: <p>Can anybody tell me what is wrong with my code and why i am getting: </p>
  
  <pre><code>Unrecognized option "entity" under "security.providers.our_users"
  </code></pre>
  
  <p>security.yml</p>
  
  <pre><code>security:
     providers:
       our_users:
          entity:
              class: AppBundle\Entity\User
  </code></pre>
  
  <p>I was using entity option many times and now im getting this error. I really dont know how to solve this. Any idea? </p>
  
  <p>Does anyone know?</p>