Receiving an alarm should not require signing up, and it should not require
pretending to be a user either: an anonymous subscriber is not an account, it
is a subscription. The row is the identity.
joinAlert now takes NO access token. The subscribe token from the QR is the
authorisation, and the service answers with a deviceToken (32 CSPRNG bytes,
base64url, stored only as SHA-256) returned exactly once. Later subscriber
calls send it as X-Device-Token (?deviceToken= on the WebSocket upgrade, which
cannot set headers): getAlert, alarmStatus, ackAlarm, removeSubscription,
qrImage and GET /ws/alarm.
The credential is deliberately narrow. It names one subscription on one alert,
so an ack addresses the ledger row directly and 'am I subscribed' is a field
comparison. createAlert/triggerAlert/disarmAlert/deleteAlert/listSubscriptions
never see it, so they keep answering 401 for a subscriber without any new gate:
owning an alert still needs an account, and the admin token stays the only
secret that can ring or silence one.
Re-joining from the same device rotates the token (one row per alert+device),
so a lost credential is recoverable with the QR and a leaked one dies on the
next join. ALARM_ANONYMOUS=false puts joinAlert back behind login and stores the
subscription against the account, exactly like rev 9.
Migration 010 is additive and idempotent: subscriber_user_id becomes nullable,
device_token_hash gets a unique index, and alarm_events.actor_user_id admits
NULL because an anonymous join logs an actor-less event.
Verified through Maestro against the dev stack (full table in
planning/platform/anonymous-access/plan.md): join with no token -> 200 and the
auth.users count does not move; getAlert/alarmStatus/ackAlarm with the token;
trigger -> 409 with the frame -> ack acked:1 destroyed:true; WS 101 with both
credentials (403 wrong subscribe token, 401 bad device token); old token 401
after a re-join; admin actions 401.
Document the wire contract as implemented: single-origin access through Maestro, no auto-stop, the owner-set persistence cap, the durable delivery ledger and its 409 check-in, explicit acks, hashed device ids, one anonymised event log, and the four ways an alert ends (delivered, expired, disarmed, deleted). Also corrects the heading to match the table it introduces.
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