api_is_author_of_blogpost.py

@api_view(['GET',])
@permission_classes((IsAuthenticated,))
def api_is_author_of_blogpost(request, slug):
	try:
		blog_post = BlogPost.objects.get(slug=slug)
	except BlogPost.DoesNotExist:
		return Response(status=status.HTTP_404_NOT_FOUND)

	data = {}
	user = request.user
	if blog_post.author != user:
		data['response'] = "You don't have permission to edit that."
		return Response(data=data)
	data['response'] = "You have permission to edit that."
	return Response(data=data)

urls.py

from django.urls import path
from blog.api.views import(
	api_detail_blog_view,
	api_update_blog_view,
	api_delete_blog_view,
	api_create_blog_view,
	api_is_author_of_blogpost,
	ApiBlogListView
)

app_name = 'blog'

urlpatterns = [
	path('<slug>/', api_detail_blog_view, name="detail"),
	path('<slug>/update', api_update_blog_view, name="update"),
	path('<slug>/delete', api_delete_blog_view, name="delete"),
	path('create', api_create_blog_view, name="create"),
	path('list', ApiBlogListView.as_view(), name="list"),
	path('<slug>/is_author', api_is_author_of_blogpost, name="is_author"),
]