Commune Subscribers API
Who receives a newsletter. Needs `audience`, and never a public surface: a newsletter's list belongs to its creator. `GET /subscriptions` is that edge read from the other end, the lists one account is on rather than the people on one list, and it needs `account: read` instead. It carries none of what a newsletter's own record of a subscriber carries: no address, no lifecycle status, none of the tags the newsletter applied and nothing about how they were acquired.