title: Django Rest Framework: @Action Route with same url_path as Viewset
body: <p>I want to POST to a DRF Viewset Detail Route. Is this possible? I know with DRF you can override the Create field, but this won't allow you to access the detail route.</p>
  
  <p>Specifically in this example I want the design of the route to be <code>POST /foo/&lt;pk&gt;/</code>, and not some route like <code>POST /foo/&lt;pk&gt;/bar/</code>.</p>
  
  <p>Here's what I want to accomplish, notice the <code>IS_THERE_A_WAY_TO_DO_THIS</code>:</p>
  
  <pre><code>class FooViewSet(
      mixins.ListModelMixin, mixins.RetrieveModelMixin, viewsets.GenericViewSet
  ):
      """
      Foo-related viewsets.
      """
  
      permission_classes = [IsAuthenticated]
      queryset = models.Foo.objects.all()
      serializer_class = serializers.FooSerializer
  
      @action(
          methods=["post"],
          detail=True,
          permission_classes=[IsAuthenticated],
          url_path="", &lt;-- IS_THERE_A_WAY_TO_DO_THIS? Normally this wont work.
          url_name="foobar",
      )
      def foobar_process(self, request, pk=None):
          pass
  </code></pre>
  
  <p>urls.py</p>
  
  <pre><code>router = DefaultRouter()
  ...
  router.register(r"foo", FooViewSet, basename="foo")
  ...
  
  urlpatterns += [
      re_path(r"^", include(router.urls)),
  ]
  
  </code></pre>