It is nice to have webhook url property to run create parameter


Current version, we need to the state of run with polling.
It may increase server and client resouce.
It is nice to set webhook url to receive a message when the state changed.
Like below

curl \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -H "Content-Type: application/json" \
  -H "OpenAI-Beta: assistants=v1" \
  -d '{
    "assistant_id": "asst_abc123"
    "webhook_url": ""

The payload is good like that

    "assistant_id": "xxx",
    "thread_id": "xxxx",
    "state": "cancelling"

What do you think?