title: Not able to delete an entity that extends another using DiscriminatorColumn due to foreign key constraint
body: <p>I am using @ORM\InheritanceType(&quot;JOINED&quot;) on my User class and i’ve created an Agent class which extends User</p>
  <p>When I try to delete the Agent entry or the corresponding User entr, I get a foreign key constraint error</p>
  <p>How can I add orphan removal?</p>
  <p>This are my User class entity settings:</p>
  <pre><code>/**
   * @ORM\Entity(repositoryClass=UserRepository::class)
   * @ORM\InheritanceType(&quot;JOINED&quot;)
   * @ORM\DiscriminatorColumn(name=&quot;discriminator&quot;, type=&quot;string&quot;)
   * @ORM\DiscriminatorMap({&quot;agent&quot; = &quot;Agent&quot;, &quot;user&quot; = &quot;User&quot;})
   * @ORM\HasLifecycleCallbacks
   */
  </code></pre>