Serves sign-up and user profiles, with what each user posted, upvoted, made, follows and invited, and the dumps and playlists under them. A user's :key is their id or @name, a current or former name in any case (resolveUserKey). A profile sent to anyone goes through toPublicUser, which drops the email. The caller's own account is routes/me.ts's.

• POST /api/users — public, with a valid invite. Creates an account, sends the welcome email, and answers the user and their tokens.
• GET /api/users?q= — public. Answers up to 8 users whose name starts with q, for @mention suggestions.
• GET /api/users/:key — public. Answers a user's profile.
• GET /api/users/:key/dumps?page=&limit=&category= — optional sign-in. Answers a page of their dumps, the private ones only to themselves, optionally in one category.
• GET /api/users/:key/dumps/:slug — optional sign-in. Answers their dump whose slug is or was slug, with its current slug; a private one 404s but for its poster.
• GET /api/users/:key/upvoted?page=&limit=&category= — optional sign-in. Answers a page of the dumps they upvoted, private ones only to themselves, optionally in one category.
• GET /api/users/:key/playlists?page=&limit=&category=&sort= — optional sign-in. Answers a page of the playlists they made, the private ones only to themselves, optionally in one playlist category, in the order sort names, as GET /api/playlists does.
• GET /api/users/:key/playlists/:slug — optional sign-in. Answers their playlist whose slug is or was slug, with its current slug and the dumps the caller may see; a private one 404s but for its owner.
• GET /api/users/:key/follow/users?page=&limit= — public. Answers a page of the users they follow.
• GET /api/users/:key/follow/playlists?page=&limit= — public. Answers a page of the public playlists they follow.
• GET /api/users/:key/invitees — public. Answers the tree of users they invited.
• GET /api/users/:key/home?path= — public. Redirects to a page of the instance a user from another instance comes from, their profile there unless path names another; a local user 404s.
• PATCH /api/users/:key/role — permission user:manage. Sets another user's role.
• PATCH /api/users/:key/username — permission user:manage. Renames a user, the caller included. It is the only way a local name changes; a user from another instance is named there (400). The instances the user signed in to are told.