I'm getting webhook for threads - but there are some issues.

How do I identify the user that the webhook is related to? I do get the post ID in the webhook - but how to find out to whom (user ID) it is related to? (i can all the API to get the threads info - but whcih token should I use - I am managing multiple users)

What are the suubscription_id":"999999999999" and "has_uid_field":false means?