add logging to debug broken conversation error

Author: andreaskoepf

backend/oasst_backend/prompt_repository.py

@@ -767,6 +767,9 @@ def trace_conversation(messages: list[Message] | dict[UUID, Message], last_messa
         while conv[-1].parent_id:
             if conv[-1].parent_id not in messages:
                 # Can't form a continuous conversation
+                logger.error(
+                    f"Broken conversation: parent of message (id={conv[-1].id}, parent_id={conv[-1].parent_id}) not found in result set"
+                )
                 raise OasstError(
                     "Broken conversation", OasstErrorCode.BROKEN_CONVERSATION, HTTPStatus.INTERNAL_SERVER_ERROR
                 )