feat: age verification with an ID document (Didit), and closed registration

Age: a Didit provider behind the vendor-neutral age interface. A person
verifies once (ID document, passive liveness, face match) and all their
linked IMVU accounts count as adult. Webhooks are checked against Didit's
signatures; only "over 18" is kept. A later answer replaces an earlier one
(an approval taken back is revoked). Checks are limited: one unfinished
check per person, 3 in 30 days, none once verified, and a monthly cap
(DIDIT_MONTHLY_LIMIT, default 30: Didit's free plan is $10 of credit a
month and a check costs $0.30). The Account page gets an Age Verification
card.

Registration: open or closed, an admin's setting in the console
(default from REGISTRATION). Closed: new accounts can only sign in until
a moderator approves them (or declines, deleting the account); the
website shows them a waiting page and the API treats them as signed out.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/api.md

@@ -17,10 +17,11 @@ is. Codes: `invalid`, `signed_out`, `forbidden`, `not_found`, `no_such_imvu_acco
 
 | | |
 | --- | --- |
-| `POST /api/auth/sign-up/email` | `{email, password, name, username}`. Usernames 3-32 of `A-Za-z0-9_`; passwords 10-256 characters. The first account is an admin. |
+| `POST /api/auth/sign-up/email` | `{email, password, name, username}`. Usernames 3-32 of `A-Za-z0-9_`; passwords 10-256 characters. The first account is an admin. With registration closed, the others wait for approval (`approved: false`): every route but `/me` answers 403 `awaiting_approval`, and the rest of the hub treats them as signed out. |
 | `POST /api/auth/sign-in/username` | `{username, password}` |
 | `POST /api/auth/sign-out` | |
-| `GET /api/v1/me` | `{person}`, with `picture`: the avatar picture of their first linked IMVU account (from IMVU, kept an hour), or `null` |
+| `GET /api/v1/me` | `{person}` (`approved` false while waiting), with `picture`: the avatar picture of their first linked IMVU account (from IMVU, kept an hour), or `null` |
+| `GET /api/v1/hub` | (anyone) `{registration}`: `open` or `closed` |
 
 ## Proxies
 
@@ -97,17 +98,20 @@ person-level providers (phone wallets, document checks) are started here.
 
 | | |
 | --- | --- |
-| `GET /api/v1/age` | `{providers: [{id, label, scope}], checks}`: the providers in use and the person's own checks |
-| `POST /api/v1/age/:provider/start` | `{returnURL}` → `{kind: "done"}`, `{kind: "redirect", url, ref}` (send the person there) or `{kind: "browser", request, ref}` (hand `request` to the browser's Digital Credentials API) |
+| `GET /api/v1/age` | `{providers: [{id, label, vendor, scope}], checks}`: the providers in use and the person's own checks (newest first; status `pending`, `complete`, `failed` or `revoked`) |
+| `POST /api/v1/age/:provider/start` | `{returnURL}` (a path on the website, or an address on it) → `{kind: "done"}`, `{kind: "redirect", url, ref}` (send the person there) or `{kind: "browser", request, ref}` (hand `request` to the browser's Digital Credentials API). An unfinished check is given again. 409 `refused`: already verified, or a limit reached (`message` says which); 502 `provider_unavailable` |
 | `POST /api/v1/age/:provider/complete` | `{ref, response}`: the browser's answer, for wallet providers |
-| `POST /api/v1/age/webhook/:provider` | the provider's webhook; the provider checks its signature |
+| `POST /api/v1/age/webhook/:provider` | the provider's webhook; the provider checks its signature (401 if it isn't the provider's). A later answer replaces an earlier one (an adult answer taken back is `revoked`) |
 
 ## Console (moderators; roles: admins)
 
 | | |
 | --- | --- |
 | `GET /api/v1/console` | `{counts, connections, online, audit}` |
-| `GET /api/v1/console/people?q=` | `{people}` |
+| `GET /api/v1/console/people?q=&waiting=true` | `{people}` (`waiting`: only accounts waiting for approval) |
+| `POST /api/v1/console/people/:id/approve` | `{person}` |
+| `POST /api/v1/console/people/:id/decline` | an account waiting for approval: deletes it |
+| `GET /api/v1/console/settings`, `PUT` (admins) | `{registration}`: `open` or `closed` (default: the API's `REGISTRATION`, else open) |
 | `GET /api/v1/console/people/:id` | `{person, links, computers}` |
 | `POST /api/v1/console/people/:id/link-cap` | `{linkCap}` (0-1000) |
 | `POST /api/v1/console/people/:id/ban` | `{reason}`; only admins ban moderators |