QfqForm will autonomously fire an lock `extend` request when the lock expired,...

QfqForm will autonomously fire an lock `extend` request when the lock expired, but a change `t_c` has been made during the lock period `t_l`. I.e. let `t_{current}` be the current time, an `extend` request is made when

    t_c + t_l > t_{current}

holds.