function scheduleAlertBeforeDue(notification,signature)
{
  new Notification(notification).actionOnDueDateAdded("actionAlertBeforeDue",signature,function(date)
  {
    date.minusDays(7);
  });
}

function actionAlertBeforeDue(notification)
{
  //If you have a Google Sheet mapping username to slack DM handle you could post
  //to the Slack API instead
  new Notification(notification).card().postComment("@card due in 1 week!");
}