To integrate a new REST API in our bulletin_board app, execute the following steps:

1. Add configurations for the Django REST Framework to the settings as shown here:

# settings.py or conf/base.py
REST_FRAMEWORK = {
    "DEFAULT_PERMISSION_CLASSES": [
        "rest_framework.permissions."
        "DjangoModelPermissionsOrAnonReadOnly"
    ],

    "DEFAULT_PAGINATION_CLASS":
        "rest_framework.pagination.LimitOffsetPagination",
    "PAGE_SIZE": 100,
}

2. In the bulletin_board app, create the serializers.py file with the following content:

# bulletin_board/serializers.py
from rest_framework import serializers

from .models import Category, Bulletin


class CategorySerializer(serializers.ModelSerializer):
    class Meta:
        model = Category
        fields = ["id", "title"]


class BulletinSerializer(serializers.ModelSerializer):
    class Meta:
        model = Bulletin
        fields = ["id", "bulletin_type", "title",
                  "description", "contact_person", "phone",
                  "email", "image", "category"]

    category = CategorySerializer()

    def create(self, validated_data):
        category_data = validated_data.pop('category')
        category, created = Category.objects.get_or_create(
            title=category_data['title'])
        bulletin = Bulletin.objects.create(category=category,
                                           **validated_data)
        return bulletin

    def update(self, instance, validated_data):
        category_data = validated_data.pop('category')
        category, created = Category.objects.get_or_create(
            title=category_data['title'])
        for fname, fvalue in validated_data.items():
            setattr(instance, fname, fvalue)
        instance.category = category
        instance.save()
        return instance

3. Add two new class-based views to the views.py file in the bulletin_board app:

# bulletin_board/views.py
from rest_framework import generics

from .models import Bulletin
from .serializers import BulletinSerializer

# ...

class RESTBulletinList(generics.ListCreateAPIView):
    queryset = Bulletin.objects.all()
    serializer_class = BulletinSerializer


class RESTBulletinDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = Bulletin.objects.all()
    serializer_class = BulletinSerializer

4. Finally, plug in the new views to the project URL configuration:

# project/urls.py
from django.urls import include, path
from bulletin_board.views import (RESTBulletinList,
                                  RESTBulletinDetail)

urlpatterns = [ 
    # ...
    path("api-auth/",
         include("rest_framework.urls",
                 namespace="rest_framework")),
    path("rest-api/bulletin-board/",
         RESTBulletinList.as_view(),
         name="rest_bulletin_list"),
    path("rest-api/bulletin-board/<int:pk>",
         RESTBulletinDetail.as_view(),
         name="rest_bulletin_detail"),
]