class OrderContentSerializer(ModelSerializer):
    class Meta:
        model = OrderContent
        fields = ('price',)




class OrderSerializer(ModelSerializer):
    order_contents = OrderContentSerializer(many=True)
    class Meta:
        model = Order
        fields = ('total_price', 'order_status', 'order_contents')
    def create(self, validated_data):
        contents_data = validated_data.pop('order_contents')
        order = Order.objects.create(**validated_data)
        for data in contents_data:
            OrderContent.objects.create(order=order, **data)
        return order

class CreateOrderCustomer(APIView):
    # permission_classes = (IsAuthenticated,)
    def post(self, request):
        print(request.data)
        serializer = serializers.OrderSerializer(data=request.data)
        print(request.data)
        if serializer.is_valid():
            print(request.data)
            print(request.user)
            serializer.save(created_by=request.user)
            return Response(data=serializer.data,status= status.HTTP_201_CREATED)
        return Response(data=serializer.errors,status=status.HTTP_400_BAD_REQUEST)

>>> from orders.serializers import OrderSerializer
>>> data={'totalprice': 3.0, 'order_status': 0, 'order_contents': [{'price': 18}, {'price': 12}]}
>>> serializer=OrderSerializer(data=data)
>>> serializer.is_valid()
True
>>> from users.models import User
>>> user=User.objects.get(username='1')
>>> serializer.save(created_by=user)
<Order: order7>