title: How to add custom permission in viewset
body: <p>How to add custom permission in viewset in django rest framework other than the default permission while creating a module?
  I have a permission "fix_an_appointment". In the below viewset, how to include this permission? Those who have this permission has only able to create. </p>
  
  <p>My views.py file:</p>
  
  <pre><code>class settingsViewSet(viewsets.ModelViewSet):
      serializer_class = SettingsSerializer
      queryset = Setting.objects.all()
  </code></pre>
  
  <p>Can anyone help?</p>