List a newsletter's chat rooms

The newsletter's chat rooms, alphabetical, each with a count of how many currently subscribed people are in it. Needs audience: read: a room is a slice of the audience, and how a creator segments their audience is not public.

Every room here is also a tag, and tag carries that id. It is the id POST /newsletters/{newsletter}/threads and PATCH /threads/{thread}/audience accept in audience_tag_ids, so this is the call to make before scoping a conversation. GET /newsletters/{newsletter}/tags?is_room=true answers the same question from the other resource and remains the one to use when you want the segment rather than the room.

Hidden rooms are in this page, carrying hidden: true. A hidden room has been withdrawn by its creator, not removed: its conversations and any article addressed to the same tag are readable by the newsletter's team and by nobody else, every member still holds the tag, and unhiding restores all of it. A collection that dropped them would make a withdrawn room indistinguishable from a removed one.

Removed rooms are not, and neither are retired tags. Removing a room clears is_room and the row stops being a room at all; a tag that was retired has had its name freed for reuse and cannot be made a room again. Either one is read under Subscriber tags, with include_retired=true for the second.