title: payload for POST and PUT methods in swagger
body: <p>im using yasg library for make a doc for my apis..
  but i have a problem:
  GET and DELETE methods are fine but when i want use POST or PUT method i cant define payload for them..
  in parameters section it says:  No parameters
  this is my code :</p>
  <pre><code>class CreateGroupView(APIView):
      def post(self, request):
          try:
              serializer = GroupSerializer(data=request.data)
              if serializer.is_valid():
                  serializer.save()
                  return Response(serializer.data, status.HTTP_201_CREATED)
              else:
                  return Response(status=status.HTTP_400_BAD_REQUEST)
          except:
              return Response({'data': 'somethings wrong'}, status.HTTP_500_INTERNAL_SERVER_ERROR)
  
  </code></pre>
  <p>what can i do?</p>