-- Web Push subscriptions. One row per browser/device push endpoint a user
-- has granted. The endpoint is globally unique (it's a per-subscription URL
-- at the push service), so re-subscribing the same browser upserts. p256dh
-- and auth are the subscription's encryption keys (base64url). Dead
-- endpoints (404/410 from the push service) are pruned on send.
CREATE TABLE IF NOT EXISTS push_subscriptions (
    id           UUID         PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id      UUID         NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    endpoint     TEXT         NOT NULL UNIQUE,
    p256dh       TEXT         NOT NULL,
    auth         TEXT         NOT NULL,
    user_agent   TEXT         NOT NULL DEFAULT '',
    created_at   TIMESTAMPTZ  NOT NULL DEFAULT now(),
    last_used_at TIMESTAMPTZ  NOT NULL DEFAULT now()
);

CREATE INDEX IF NOT EXISTS push_subscriptions_user_idx
    ON push_subscriptions (user_id);