✨(backend) add comment viewset

This commit add the CRUD part to manage comment lifeycle. Permissions
are relying on the Document and Comment abilities. Comment viewset
depends on the Document route and is added to the
document_related_router. Dedicated serializer and permission are
created.

src/backend/core/api/viewsets.py

@@ -2150,3 +2150,36 @@ class ConfigView(drf.views.APIView):
             )
 
         return theme_customization
+
+
+class CommentViewSet(
+    viewsets.ModelViewSet,
+):
+    """API ViewSet for comments."""
+
+    permission_classes = [permissions.CommentPermission]
+    queryset = models.Comment.objects.select_related("user", "document").all()
+    serializer_class = serializers.CommentSerializer
+    pagination_class = Pagination
+    _document = None
+
+    def get_document_or_404(self):
+        """Get the document related to the viewset or raise a 404 error."""
+        if self._document is None:
+            try:
+                self._document = models.Document.objects.get(
+                    pk=self.kwargs["resource_id"],
+                )
+            except models.Document.DoesNotExist as e:
+                raise drf.exceptions.NotFound("Document not found.") from e
+        return self._document
+
+    def get_serializer_context(self):
+        """Extra context provided to the serializer class."""
+        context = super().get_serializer_context()
+        context["resource_id"] = self.kwargs["resource_id"]
+        return context
+
+    def get_queryset(self):
+        """Return the queryset according to the action."""
+        return super().get_queryset().filter(document=self.kwargs["resource_id"])