Function queue_approval 

pub fn queue_approval(
    queue: &Arc<Mutex<Vec<QueuedApproval>>>,
    record: QueuedApproval,
) -> Option<usize>

Append one record to a parent’s audit queue and return its stable index.

The queue is append-only for the life of the process, so the index stays valid for record_queued_outcome. None means the record could not be stored and no outcome should be written back.