Commune Team API
Who may act on behalf of a newsletter: its owner, plus the members the owner added as admins, editors or guests. Both sides of that edge are here. A newsletter's roster answers "who is on this team" and needs `settings`. `GET /memberships` answers "which teams is this account on", which is the same membership read from the person rather than from the newsletter, and needs `account: read` instead: the set of teams somebody is on is a fact about them.