Ensure we allow application/problem+json as a valid Accept header…

… value in v2

Ticket: RHCLOUD-35321

Since we are starting to use `application/problem+json` as a response content type
in v2 APIs [1], we need RBAC/Django to accept this as a valid `Accept` header value,
given clients built off the API spec will be sending this.

Currently, if you send a request to `/api/rbac/v2/workspaces/<uuid>/ -XDELETE -H 'Accept: application/problem+json'`
which is what a client built off the spec will do (with the `Accept` header),
you'll get an error from RBAC: "Not acceptable 406".

We _do_ set the correct `content-type` to align with the spec [2], however Django
complains becasue it can't find the `application/problem+json` renderer.

This implements a custom renderer in Django Rest Framework [3] on the v2 views,
specifically workspaces now, specifying it in the `renderer_classes` of the view,
and setting the `media_type` (used to match the `Accept` value(s) to a renderer)
and `format` (response) properties accordingly.

The `DELETE` test was modified prior to this change to add `Accept: application/problem+json`
to confirm it failed (it did), and now succeeds with the changes in place.

[1] [https://github.com/RedHatInsights/insights-rbac/blob/master/docs/source/specs/v2/openapi.v2.yaml]
[2] https://github.com/RedHatInsights/insights-rbac/blob/master/rbac/api/common/exception_handler.py#L93
[3] [https://www.django-rest-framework.org/api-guide/renderers/#custom-renderers]

rbac/api/common/renderers.py

@@ -0,0 +1,26 @@
+#
+# Copyright 2024 Red Hat, Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+"""Shared DRF renderers."""
+from rest_framework.renderers import JSONRenderer
+
+
+class ProblemJSONRenderer(JSONRenderer):
+    """Renderer for accepting application/problem+json in Accept header."""
+
+    media_type = "application/problem+json"
+    format = "json"

rbac/management/workspace/view.py

@@ -23,7 +23,9 @@
 from management.utils import validate_uuid
 from rest_framework import mixins, serializers, viewsets
 from rest_framework.filters import OrderingFilter
+from rest_framework.settings import api_settings
 
+from api.common.renderers import ProblemJSONRenderer
 from .model import Workspace
 from .serializer import WorkspaceSerializer
 
@@ -50,6 +52,7 @@ class WorkspaceViewSet(
     queryset = Workspace.objects.annotate()
     lookup_field = "uuid"
     serializer_class = WorkspaceSerializer
+    renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES + [ProblemJSONRenderer]
     ordering_fields = ("name",)
     ordering = ("name",)
     filter_backends = (filters.DjangoFilterBackend, OrderingFilter)

tests/management/workspace/test_view.py

@@ -410,6 +410,7 @@ def test_delete_workspace(self):
 
         url = reverse("workspace-detail", kwargs={"uuid": workspace.uuid})
         client = APIClient()
+        self.headers["HTTP_ACCEPT"] = "application/problem+json"
         response = client.delete(url, None, format="json", **self.headers)
 
         self.assertEqual(response.status_code, status.HTTP_204_NO_CONTENT)