title: Django related models also need a generic relation: how to work around unresolved reference?
body: <p>Here is the two models:</p>
  <pre><code>class Circuit(models.Model):
      uuid = models.UUIDField(default=uuid.uuid4, editable=False, unique=True)
      service_order_item = models.ForeignKey(ServiceOrderItem, on_delete=models.RESTRICT)
      location_a = models.ForeignKey(Location, on_delete=models.SET_NULL, blank=True, null=True)
      location_z = models.ForeignKey(Location, on_delete=models.SET_NULL, blank=True, null=True)
  
  
  class CircuitItem(models.Model):
      circuit = models.ForeignKey(Circuit, on_delete=models.CASCADE)
      index = models.IntegerField(default=0)
  
      content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
      object_id = models.PositiveIntegerField()
      content_object = GenericForeignKey()
  </code></pre>
  <p><code>CircuitItems</code> are list of things in a circuit
  the problem is <code>CircuitItems</code> can be <code>Circuits</code> themselves (as well as some other models)</p>
  <p>Is it possible to do something like:<br>
  <code>circuit_link = GenericRelation(&quot;CircuitItem&quot;)</code><br>
  to avoid the unresolved reference, or is there no way to do this with only two tables and a third will be required?</p>