fix: read status not updating in mongo backend

forum/backends/mongodb/api.py

@@ -1046,6 +1046,15 @@ def create_comment(cls, data: dict[str, Any]) -> str:
             parent_id=data.get("parent_id"),
         )
 
+        # Update thread's last activity timestamp to mark it as having new activity
+        comment_thread_id = data.get("comment_thread_id")
+        if comment_thread_id:
+            CommentThread().update(
+                comment_thread_id,
+                last_activity_at=datetime.now(),
+                skip_timestamp_update=True
+            )
+
         if data.get("parent_id"):
             cls.update_stats_for_course(data["author_id"], data["course_id"], replies=1)
         else:

forum/backends/mongodb/threads.py

@@ -204,6 +204,7 @@ def update(
         close_reason_code: Optional[str] = None,
         closed_by_id: Optional[str] = None,
         group_id: Optional[int] = None,
+        last_activity_at: Optional[datetime] = None,
         skip_timestamp_update: bool = False,
     ) -> int:
         """
@@ -258,6 +259,7 @@ def update(
             ("close_reason_code", close_reason_code),
             ("closed_by_id", closed_by_id),
             ("group_id", group_id),
+            ("last_activity_at", last_activity_at),
         ]
         update_data: dict[str, Any] = {
             field: value for field, value in fields if value is not None