✨(back) new endpoint document can_edit

The endpoint can_edit is added to the DocumentViewset, it will give the
information to the frontend application id the current user can edit the
Docs based on the no-websocket rules.

src/backend/core/api/viewsets.py

@@ -635,54 +635,76 @@ class DocumentViewSet(
         """Override to implement a soft delete instead of dumping the record in database."""
         instance.soft_delete()
 
-    def perform_update(self, serializer):
-        """Check rules about collaboration."""
-        if serializer.validated_data.get("websocket"):
-            return super().perform_update(serializer)
-
+    def _can_user_edit_document(self, document_id, set_cache=False):
+        """Check if the user can edit the document."""
         try:
-            connection_info = CollaborationService().get_document_connection_info(
-                serializer.instance.id,
+            count, exists = CollaborationService().get_document_connection_info(
+                document_id,
                 self.request.session.session_key,
             )
         except requests.HTTPError as e:
-            capture_exception(e)
-            connection_info = {
-                "count": 0,
-                "exists": False,
-            }
+            logger.exception("Failed to call collaboration server: %s", e)
+            count = 0
+            exists = False
 
-        if connection_info["count"] == 0:
-            # No websocket mode
+        if count == 0:
+            # Nobody is connected to the websocket server
             logger.debug("update without connection found in the websocket server")
-            cache_key = f"docs:no-websocket:{serializer.instance.id}"
+            cache_key = f"docs:no-websocket:{document_id}"
             current_editor = cache.get(cache_key)
-            if not current_editor:
-                cache.set(
-                    cache_key,
-                    self.request.session.session_key,
-                    settings.NO_WEBSOCKET_CACHE_TIMEOUT,
-                )
-            elif current_editor != self.request.session.session_key:
-                raise drf.exceptions.PermissionDenied(
-                    "You are not allowed to edit this document."
-                )
-            cache.touch(cache_key, settings.NO_WEBSOCKET_CACHE_TIMEOUT)
-            return super().perform_update(serializer)
 
-        if connection_info["exists"]:
-            # Websocket mode
+            if not current_editor:
+                if set_cache:
+                    cache.set(
+                        cache_key,
+                        self.request.session.session_key,
+                        settings.NO_WEBSOCKET_CACHE_TIMEOUT,
+                    )
+                return True
+
+            if current_editor != self.request.session.session_key:
+                return False
+
+            if set_cache:
+                cache.touch(cache_key, settings.NO_WEBSOCKET_CACHE_TIMEOUT)
+            return True
+
+        if exists:
+            # Current user is connected to the websocket server
             logger.debug("session key found in the websocket server")
-            return super().perform_update(serializer)
+            return True
 
         logger.debug(
             "Users connected to the websocket but current editor not connected to it. Can not edit."
         )
 
+        return False
+
+    def perform_update(self, serializer):
+        """Check rules about collaboration."""
+        if serializer.validated_data.get("websocket", False):
+            return super().perform_update(serializer)
+
+        if self._can_user_edit_document(serializer.instance.id, set_cache=True):
+            return super().perform_update(serializer)
+
         raise drf.exceptions.PermissionDenied(
             "You are not allowed to edit this document."
         )
 
+    @drf.decorators.action(
+        detail=True,
+        methods=["get"],
+        url_path="can-edit",
+    )
+    def can_edit(self, request, *args, **kwargs):
+        """Check if the current user can edit the document."""
+        document = self.get_object()
+
+        return drf.response.Response(
+            {"can_edit": self._can_user_edit_document(document.id)}
+        )
+
     @drf.decorators.action(
         detail=False,
         methods=["get"],