title: Django admin GenericForeignKey inline
body: <pre><code>class MyUser(AbstractBaseUser):
      ...
      content_type = models.ForeignKey(ContentType, limit_choices_to={"model__in": ("agentprofile", "clientprofile"))
      object_id = models.PositiveIntegerField()
      profile = generic.GenericForeignKey('content_type', 'object_id')
  
  class AgentProfile(models.Model):
      license_number = models.CharField(max_length=50, blank=True)
  
  class ClientProfile(models.Model):
      address = models.CHarField(max_length=250)
  </code></pre>
  
  <p>I have 3 models: MyUser(custom user model), ClientProfile, AgentProfile. How can I edit ClientProfile/AgentProfile on MyUser admin page (like inline)?</p>