feat(hint): target groups and automatic hints, V30

Hint targets combined with AND: without Steam, role and higher, new
users by registration_date, empty library flag. Four automatic hints
(NO_STEAM, EMPTY_LIBRARY, PILE_GREW, LINK_QUEUE), on by default; the
admin turns each on or off (audited). Users snooze one for 7 days (X)
or hide it for good (tick), stored on the server. Hint text may use
**bold** and [text](url).

readme.md

@@ -80,6 +80,13 @@ To Be Played is split into three repositories:
   and end time, type `DISMISS` or `ACCEPT`). The dashboard shows the running hints one at a time, newest first.
   "Do not show again" on a `DISMISS` hint or "OK" on an `ACCEPT` hint is a row in `hint_done`, so the hint never
   comes back for this user on any device. Creating and ending a hint are rows in `admin_audit`.
+  A hint can target groups, combined with AND (none = all users): without Steam, role (this role and higher, by the
+  active role of the token), new users (`users.registration_date` less than N days ago), empty library (Auth only
+  sends a flag; the Frontend checks it with Core). The text may use `**bold**` and `[text](url)`; the Frontend
+  renders it, never as HTML. Four automatic hints (`NO_STEAM`, `EMPTY_LIBRARY`, `PILE_GREW`, `LINK_QUEUE`) are on
+  by default; a PLATFORM_ADMIN turns each on or off (`auto_hint`, audited). `GET /api/hints` lists the keys that are
+  on and not hidden for the user; the Frontend checks the conditions. X hides one for 7 days, "Do not show again"
+  for good (`auto_hint_hidden`).
 - **What's new**: a PLATFORM_ADMIN publishes news entries (plain text, English, German optional; edit and delete, no
   drafts). The dashboard shows the entries published after `user_settings.news_seen_at` once in a dialog; "Got it"
   sets the stamp to now (`PUT /api/news/seen`). A new user starts at the registration time. `/whats-new` lists all
@@ -129,11 +136,14 @@ To Be Played is split into three repositories:
 | `DELETE` | `/api/admin/users/{id}` (`409 SELF_ACTION`, `TARGET_IS_ADMIN`, `TARGET_IS_PENDING`, `TARGET_IS_UNCONFIRMED`) | PLATFORM_ADMIN |
 | `DELETE` | `/api/admin/users/{id}/unconfirmed` (hard delete of an unconfirmed request; `204`; `404`; `409 NOT_UNCONFIRMED`, `SELF_ACTION`, `TARGET_IS_ADMIN`) | PLATFORM_ADMIN |
 | `POST` | `/api/admin/users/{id}/password-reset` (`204`; `409 NOT_ACTIVE`, `SELF_ACTION`, `TARGET_IS_ADMIN`) | PLATFORM_ADMIN |
-| `GET` | `/api/hints` (`{results}`: running hints not closed for good, newest first) | access token |
+| `GET` | `/api/hints` (`{results}`: running hints for this user not closed for good, newest first, with `emptyLibraryOnly`; `automatic`: keys of the automatic hints that are on and not hidden) | access token |
+| `PUT` | `/api/hints/auto/{key}/snooze` (hide 7 days; `204`; `404 HINT_NOT_FOUND`) | access token |
+| `PUT` | `/api/hints/auto/{key}/done` (hide for good; `204`; `404 HINT_NOT_FOUND`) | access token |
 | `PUT` | `/api/hints/{id}/done` (`204`; `404 HINT_NOT_FOUND`) | access token |
-| `GET` | `/api/admin/hints` (`{results}` with `status` PLANNED/ACTIVE/ENDED by the server clock and `doneCount`, newest first) | PLATFORM_ADMIN |
-| `POST` | `/api/admin/hints` (`{textEn, textDe, kind, startsAt, endsAt}`; `201 {id}`, `400 INVALID_HINT`) | PLATFORM_ADMIN |
+| `GET` | `/api/admin/hints` (`{results}` with `status` PLANNED/ACTIVE/ENDED by the server clock and `doneCount` and the `target*` fields, newest first; `automatic`: `[{key, enabled}]`) | PLATFORM_ADMIN |
+| `POST` | `/api/admin/hints` (`{textEn, textDe, kind, startsAt, endsAt}` and optional `targetNoSteam`, `targetRole` (this role and higher), `targetNewDays` (1-365), `targetEmptyLibrary`; `201 {id}`, `400 INVALID_HINT` for the time range; `400 VALIDATION_FAILED` for a bad `targetNewDays` or `targetRole`) | PLATFORM_ADMIN |
 | `PUT` | `/api/admin/hints/{id}/end` (`204`; a planned hint never starts) | PLATFORM_ADMIN |
+| `PUT` | `/api/admin/hints/auto/{key}` (`{enabled}`; `204`; `404 HINT_NOT_FOUND`) | PLATFORM_ADMIN |
 | `GET` | `/api/news` (`{results}` with `seen`, newest first) | access token |
 | `PUT` | `/api/news/seen` (`204`) | access token |
 | `GET` | `/api/admin/news` (`{results}`, newest first) | PLATFORM_ADMIN |