List a newsletter's articles

The newsletter's articles, most recently published first, ordered by posted_at descending with articles that never got a date last.

Two gates apply and neither can be turned off. An article stamped with an audience is returned only to a credential that may read that audience: the newsletter's owner, an admin or editor, or a subscriber holding one of the article's tags. An article whose posted_at is in the future is not returned at all until that moment passes, so a scheduled article never leaks early through this collection.

content is never included here, whatever ?fields= asks for. An article body is large enough that returning a page of them is the wrong default, so read it from GET /articles/{article}.