title: Sonata Admin list custom query for ListMapper sonata_type_model field
body: <p>I try to get some entrys which match with all of my step objects but I don't have direct relation beetween them so I need to use a custom query.</p>
  
  <p>I tried that in my admin class :</p>
  
  <pre><code>    protected function configureListFields(ListMapper $listMapper)
  {
      $listMapper
          -&gt;addIdentifier('texteEtape', null, array('label' =&gt; $this-&gt;getTranslator()-&gt;trans('label.step.text')));
  
      $this-&gt;addCountryListMap($listMapper);
  
      $listMapper
          -&gt;addIdentifier('id')
          -&gt;add('temperature')
          -&gt;add('rincage', null, array('label' =&gt; $this-&gt;getTranslator()-&gt;trans('label.rinsing')))
          -&gt;add('concentration')
          -&gt;add('temps', null, array('label' =&gt; $this-&gt;getTranslator()-&gt;trans('label.time')))
          -&gt;add('produit', null, array('label' =&gt; $this-&gt;getTranslator()-&gt;trans('label.product')))
          -&gt;add('enabled', null, array('editable' =&gt; true))
          -&gt;add('_action', 'actions', array(
              'actions' =&gt; array(
                  'edit' =&gt; array(),
                  'delete' =&gt; array()
              )
          ))
          -&gt;add('updatedAt')
          -&gt;add('Protocols','sonata_type_model', array('required' =&gt; true,
              'class'=&gt; 'HypredMainBundle:Protocole','property'=&gt; 'name',
              'query_builder' =&gt; $this-&gt;getProtocoles($listMapper-&gt;get('id'))));
  </code></pre>
  
  <p>The getProtocoles function :</p>
  
  <pre><code>    private function getProtocoles($id) {
      $querybuilder = $this-&gt;getManager()-&gt;getRepository('HypredMainBundle:Etape')-&gt;getStepProtocoles($id);
  
      var_dump($querybuilder-&gt;getQuery()-&gt;getResult());
      die();
  
      return $querybuilder;
  }
  </code></pre>
  
  <p>I would like to know how pass current entity id also (identifier return a FieldDescription object).</p>
  
  <p>Maybe I miss something or something, I hope my post is comprehensive.</p>
  
  <p>Thanks in advance for your time.</p>