code: function hashKey(requestorId, taskId) {
    var sha       = crypto.createHash('sha512');
    sha.update(requestorId);
    sha.update(taskId);
  
    return sha.digest('hex');
  }
docs: Generate a unique hash from the given requestor and task identifiers.
  ---------------------------------------------------------------------
  @param {string} requestorId
  @param {string} taskId
  @return {string}
  @api {private}