♻️(backend) simplify ResourceAccess viewset implementation

Restructure ResourceAccess viewset to align with Room and Recording viewset
patterns. Clean up implementation while preserving identical behavior and
API contract. Improves code consistency and maintainability across related
viewsets.

ResourceAccessPermission inherits from IsAuthenticated.

src/backend/core/api/viewsets.py

@@ -531,40 +531,12 @@ class RoomViewSet(
         )
 
 
-class ResourceAccessListModelMixin:
-    """List mixin for resource access API."""
-
-    def get_permissions(self):
-        """User only needs to be authenticated to list rooms access"""
-        if self.action == "list":
-            permission_classes = [permissions.IsAuthenticated]
-        else:
-            return super().get_permissions()
-
-        return [permission() for permission in permission_classes]
-
-    def get_queryset(self):
-        """Return the queryset according to the action."""
-        queryset = super().get_queryset()
-        if self.action == "list":
-            user = self.request.user
-            queryset = queryset.filter(
-                Q(resource__accesses__user=user),
-                resource__accesses__role__in=[
-                    models.RoleChoices.ADMIN,
-                    models.RoleChoices.OWNER,
-                ],
-            ).distinct()
-        return queryset
-
-
 class ResourceAccessViewSet(
-    ResourceAccessListModelMixin,
     mixins.CreateModelMixin,
     mixins.DestroyModelMixin,
-    mixins.ListModelMixin,
     mixins.RetrieveModelMixin,
     mixins.UpdateModelMixin,
+    mixins.ListModelMixin,
     viewsets.GenericViewSet,
 ):
     """
@@ -575,6 +547,25 @@ class ResourceAccessViewSet(
     queryset = models.ResourceAccess.objects.all()
     serializer_class = serializers.ResourceAccessSerializer
 
+    def get_queryset(self):
+        """Return the queryset according to the action."""
+
+        queryset = super().get_queryset()
+
+        # Restrict access to resources the user either has explicit
+        # permissions for or administrative privileges over.
+        if self.action == "list":
+            user = self.request.user
+            queryset = queryset.filter(
+                Q(resource__accesses__user=user),
+                resource__accesses__role__in=[
+                    models.RoleChoices.ADMIN,
+                    models.RoleChoices.OWNER,
+                ],
+            ).distinct()
+
+        return queryset
+
 
 class RecordingViewSet(
     mixins.DestroyModelMixin,