ALTER TABLE alerts ADD COLUMN acknowledged_by INTEGER REFERENCES users(id) ON DELETE SET NULL;
ALTER TABLE alerts ADD COLUMN acknowledged_at INTEGER;

CREATE TABLE alert_comments (
    id         INTEGER PRIMARY KEY AUTOINCREMENT,
    alert_id   INTEGER NOT NULL REFERENCES alerts(id)  ON DELETE CASCADE,
    user_id    INTEGER NOT NULL REFERENCES users(id)   ON DELETE CASCADE,
    content    TEXT    NOT NULL,
    created_at INTEGER NOT NULL DEFAULT (strftime('%s', 'now'))
);

CREATE INDEX alert_comments_alert_id_idx ON alert_comments(alert_id);