Return Triggered Stop Sequence

It would be extremely useful if the API response contained *which* stop sequence was triggered if there are multiple listed. For example, if you have the model's default stop sequence and a custom one which you want to trigger an action, you currently need to carefully choose the text leading up to it so you can determine if it was the custom stop sequence or not. It would be way easier to do this sort of thing if the api simply told you which stop sequence was triggered instead of `"done_reason": "stop"`.