Set one lock per account for push notif

    public static HashMap<String, List<String>> pushed_notifications = new HashMap<>();

    public static ReentrantLock lock = new ReentrantLock();

    private static final HashMap<String, ReentrantLock> lockMap = new HashMap<>();

    private static ReentrantLock getLock(String slug) {

        synchronized (lockMap) {

            if (lockMap.containsKey(slug)) {

                return lockMap.get(slug);

            }

            ReentrantLock lock = new ReentrantLock();

            lockMap.put(slug, lock);

            return lock;

        }

    }

    public static synchronized void task(Context context, String slug) throws DBException {

        }

        new Thread(() -> {

            ReentrantLock lock = getLock(slug);

            try {

                // fetch if we get the lock, or ignore, another thread is doing the job

                if (lock.tryLock()) {