title: Django REST Framework after PUT/PATCH action
body: <p>I want to make some actions after an api's PUT/PATCH process is completed. </p>
  
  <p>My API updates some values of one Model but after these Updates I want to Update another Model values taking  the info sent of the API.</p>
  
  <p>For Example:</p>
  
  <pre><code>class Model1(models.Model):
      name = models.CharField(max_length=140)
      qty = models.IntegerField(default=0)
  
  class Model2(models.Model):
      val = models.CharField(max_length=15)
  </code></pre>
  
  <p>I have this models, so, my API updates Model1.qty value with a PATCH call. Then I want to Update the Model2.val value with the data of the PATCH call to my API that actually is equals to Model1.qty value</p>
  
  <p>I dont know exactly how to do this but I think I should Override the "update" method.</p>
  
  <pre><code>def update(self, request, *args, **kwargs):
      ...??
  def partial_update(self, request, *args, **kwargs):
      ...??
  </code></pre>
  
  <p>Any Ideas?</p>
  
  <p><strong>NOTE</strong> Im using HyperlinkedModelSerializers, ModelViewSets and Routers to make my API works.</p>