docs: def post(self, request, *args, **kwargs):
          """
          Adds new product to the current shopping cart
          """
          POST = json.loads(request.body.decode('utf-8'))
  
          if 'product_pk' in POST and 'quantity' in POST:
              cart = ShoppingCartProxy(request)
              cart.add(
                  product_pk=int(POST['product_pk']),
                  quantity=int(POST['quantity'])
              )
              return JsonResponse(cart.products)
  
          return HttpResponseBadRequest()