title: Django Rest Framework - AssertionError Fix your URL conf, or set the `.lookup_field` attribute on the view correctly
body: <p>I'm trying to return as single object (not a queryset) that is specific to a user without them having to specify an identifier/pk within the requested URL. Each user has an organisation FK.</p>
  
  <p>i.e. <a href="http://website/organisation" rel="noreferrer">http://website/organisation</a> and not <a href="http://website/organisation/1" rel="noreferrer">http://website/organisation/1</a></p>
  
  <p>I'm receiving the following error, since it's expecting this identifier:
  <code>AssertionError: Expected view OrganisationDetail to be called with a URL keyword argument named "user__organisation_id". Fix your URL conf, or set the</code>.lookup_field<code>attribute on the view correctly.</code></p>
  
  <p><strong>How/What do I need to specify when using the RetrieveModelMixin/GenericAPIViewso that it returns a singular object linked by a FK?</strong></p>
  
  <p>My view class:</p>
  
  <pre><code>class OrganisationDetail(mixins.RetrieveModelMixin, mixins.UpdateModelMixin,generics.GenericAPIView):
      serializer_class = OrganisationDetailSerializer
      lookup_field = 'pk' #yes, I know this is the default and there's no need to speciy
  
      def get_queryset(self):
          return Organisation.objects.filter(pk=self.request.user.organisation_id)
  
      def get(self, request, *args, **kwargs):
          return self.retrieve(request, *args, **kwargs)
  
      def put(self, request, *args, **kwargs):
          return self.update(request, *args, **kwargs)
  </code></pre>
  
  <p>Related url:
  <code>url(r'^api/v1/organisation/$', OrganisationDetail.as_view()),</code></p>
  
  <p>My model:</p>
  
  <pre><code>class Person(AbstractUser):
      organisation = models.ForeignKey(Organisation, related_name='members', null=True)
      is_admin = models.BooleanField(default=False)
      def __str__(self):
          return self.first_name + " " + self.last_name + " - " + self.email
  </code></pre>