Meanings of user identifiers

API Endpoint(s) and/or Zoom API Event(s)
GET/past_meetings/{meetingId}/participants

Description
Not sure about the meaning of various user identifiers, returned by this API.
id
user_id
registrant_id

Can you please provide their definitions? And comment on the behavior (like whether these identifiers persist across multiple meetings, whether these identifiers allow to look up the user later after meeting is over/deleted, etc)

Answered at the Zoom Developer office hours today, thank you!