add functionality to clone shared chats

backend/open_webui/models/chats.py

@@ -469,6 +469,8 @@ class ChatTable:
     def get_chat_by_share_id(self, id: str) -> Optional[ChatModel]:
         try:
             with get_db() as db:
+                # it is possible that the shared link was deleted. hence,
+                # we check if the chat is still shared by checkng if a chat with the share_id exists
                 chat = db.query(Chat).filter_by(share_id=id).first()
 
                 if chat: