models.py

from django.db.models import ForeignKey, CASCADE, SET_NULL, ManyToManyField
from django.utils.translation import ugettext_lazy as _

from model_utils.fields import StatusField
from model_utils import Choices

from example.core.models import BaseModel, HashableModel


class Order(BaseModel, HashableModel):  # type: ignore

    client = ForeignKey(
        "clients.Client",
        on_delete=CASCADE,
        related_name="orders",
        verbose_name=_("Client"),
    )
    master = ForeignKey(
        "masters.Master",
        on_delete=SET_NULL,
        related_name="orders",
        verbose_name=_("Master"),
        null=True
    )

    services = ManyToManyField("services.Service")


class OrderProposal(BaseModel, HashableModel):  # type: ignore

    STATUS = Choices(
        ("approved", _("Published")),
        ("waiting", _("Waiting")),
        ("canceled", _("Canceled"))
    )

    status = StatusField(default="approved")

    order = ForeignKey(
        "orders.Order",
        on_delete=CASCADE,
        related_name="proposals",
        verbose_name=_("Order")
    )

    master = ForeignKey(
        "masters.Master",
        on_delete=CASCADE,
        related_name="proposals",
        verbose_name=_("Master")
    )

serializers.py

from rest_framework.serializers import ModelSerializer

from example.core.serializers import HashableModelSerializerMixin
from example.clients.serializers import ClientSerializer
from example.masters.serializers import MasterSerializer
from example.services.serializers import ServiceSerializer
from example.orders.models import Order, OrderProposal


class OrderProposalSerializer(HashableModelSerializerMixin, ModelSerializer):

    master = MasterSerializer()

    class Meta:
        model = OrderProposal
        exclude = ("is_removed", "order")


class OrderSerializer(HashableModelSerializerMixin, ModelSerializer):

    client = ClientSerializer()
    master = MasterSerializer()

    services = ServiceSerializer(many=True, read_only=True)
    proposals = OrderProposalSerializer(many=True)

    class Meta:
        model = Order
        exclude = ("is_removed", )

views.py

from rest_framework.viewsets import ReadOnlyModelViewSet

from example.orders.models import Order
from example.orders.serializers import OrderSerializer


class OrderViewSet(ReadOnlyModelViewSet):

    queryset = Order.objects.prefetch_related("proposals").all()
    serializer_class = OrderSerializer