API: adhere to Bugsink's DB-transactional model

as per https://www.bugsink.com/blog/database-transactions/

projects/api_views.py

@@ -2,7 +2,7 @@ from django.shortcuts import get_object_or_404
 from rest_framework import viewsets
 
 from bugsink.api_pagination import AscDescCursorPagination
-from bugsink.api_mixins import ExpandViewSetMixin
+from bugsink.api_mixins import ExpandViewSetMixin, AtomicRequestMixin
 
 from .models import Project
 from .serializers import (
@@ -20,7 +20,7 @@ class ProjectPagination(AscDescCursorPagination):
     default_direction = "asc"
 
 
-class ProjectViewSet(ExpandViewSetMixin, viewsets.ModelViewSet):
+class ProjectViewSet(AtomicRequestMixin, ExpandViewSetMixin, viewsets.ModelViewSet):
     """
     /api/canonical/0/projects/
     GET /projects/           → list ordered by name ASC, hides soft-deleted, optional ?team=<uuid> filter

projects/test_api.py

@@ -1,4 +1,4 @@
-from django.test import TestCase as DjangoTestCase
+from bugsink.test_utils import TransactionTestCase25251 as TransactionTestCase
 from django.urls import reverse
 from rest_framework.test import APIClient
 
@@ -7,7 +7,7 @@ from teams.models import Team
 from projects.models import Project
 
 
-class ProjectApiTests(DjangoTestCase):
+class ProjectApiTests(TransactionTestCase):
     def setUp(self):
         self.client = APIClient()
         token = AuthToken.objects.create()
@@ -77,7 +77,7 @@ class ProjectApiTests(DjangoTestCase):
         self.assertEqual(r.status_code, 405)
 
 
-class ExpansionTests(DjangoTestCase):
+class ExpansionTests(TransactionTestCase):
     """
     Expansion tests are exercised via ProjectViewSet, but the intent is to validate the
     generic ExpandableSerializerMixin infrastructure.