title: JMS serializer and gedmo softdeleteable not work with relation entities
body: <p>I'm using the Gedmo SoftDeletable filter for Symfony2 and Doctrine (<a href="https://github.com/l3pp4rd/DoctrineExtensions/blob/master/doc/softdeleteable.md" rel="nofollow noreferrer">https://github.com/l3pp4rd/DoctrineExtensions/blob/master/doc/softdeleteable.md</a>)</p>
  
  <p>I'm also using the JMSSerializerBundle to serialize reponses to JSON for my REST API.</p>
  
  <p>How to tell jms serializer annotation group about softdeleteable filters ? </p>
  
  <p>And when my response contain entity which have relation with entity which have <code>deleted_at</code> field not empty I have error</p>
  
  <pre><code>Entity of type 'AppBundle\Entity\Courses' for IDs id(2) was not found
  </code></pre>
  
  <p>because <code>sub_cources</code>, example id 1 have relation with <code>courses</code> in example id 2 and  <code>courses</code> with id 2 have not empty deleted_at - removed entity </p>
  
  <p>example I have </p>
  
  <pre><code>/**
   * @ORM\HasLifecycleCallbacks
   * @ORM\Table(name="sub_cources")
   *@ORM\Entity(repositoryClass="AppBundle\Entity\Repository\SubCoursesRepository")
   * @Gedmo\SoftDeleteable(fieldName="deletedAt")
   * @AssertBridge\UniqueEntity(
   *     groups={"post_sub_course", "put_sub_course"},
   *     fields="name",
   *     errorPath="not valid",
   *     message="This name is already in use."
   * )
   */
  class SubCourses
  
  
      /**
   * @var Courses
   *
   * @ORM\ManyToOne(targetEntity="AppBundle\Entity\Courses", inversedBy="subCourses")
   * @Annotation\Groups({
   *     "get_sub_courses"
   * })
   * @Annotation\Type("AppBundle\Entity\Courses")
   */
  private $courses;
  </code></pre>
  
  <p>my action</p>
  
  <pre><code>            return $this-&gt;createSuccessResponse(
              [
                  'sub_courses' =&gt; $subCourses-&gt;getEntitiesByParams($paramFetcher),
                  'total' =&gt; $subCourses-&gt;getEntitiesByParams($paramFetcher, true),
              ],
              ['get_sub_courses'],
              true
          );
  </code></pre>
  
  <p>And my response look like </p>
  
  <pre><code>    /**
   * @param $data
   * @param null|array $groups
   * @param null|bool  $withEmptyField
   *
   * @return View
   */
  protected function createSuccessResponse($data, array $groups = null, $withEmptyField = null)
  {
      $context = SerializationContext::create()-&gt;enableMaxDepthChecks();
      if ($groups) {
          $context-&gt;setGroups($groups);
      }
  
      if ($withEmptyField) {
          $context-&gt;setSerializeNull(true);
      }
  
      return View::create()
          -&gt;setStatusCode(self::HTTP_STATUS_CODE_OK)
          -&gt;setData($data)
          -&gt;setSerializationContext($context);
  }
  </code></pre>
  
  <p>How to tell jms serializer annotation group about softdeleteable filters ? </p>