Start a thread in MR

It will be cool to start a thread instead of comment in a MR.
This action will allow the bot to block the merge until the thread is resolved by anyone.

We can imagine a thread action (like the comment action):

merge_requests:
    rules:
      - name: No labels
        conditions:
          state: opened
          forbidden_labels:
            - "Status: Incomplete"
        actions:
          labels:
            - "Status: Incomplete"
          thread: |
            {{author}}, you should add at least a label to this MR.  
            Add one and resolve this thread.