title: How to list available ViewSet actions in Django-Rest-Framework?
body: <p>I've added a custom action to a Viewset, via "@detail_route". Is there some way to list any custom actions?</p>
  
  <pre><code>class MyViewSet(viewsets.ModelViewSet):
      ...
      @detail_route(methods=['post'])
      def my_action(self, request, pk=None):
          ...
  </code></pre>
  
  <p>What I would like to happen (e.g.):</p>
  
  <pre><code>curl 127.0.0.1/api/whatever/1/?format=json
  &gt;&gt;&gt; {'actions':{'my_action':'/api/whatever/1/my_action'},...}
  </code></pre>
  
  <p>Like-wise, does the API format have a mechanism to display that information?</p>