Enabling the user to acknowledge the article delivery

If the user receives the items, then he/she clicks on the link to acknowledge. The same published URL is used this time too with an additional delivered query string.

For example:

https://script.google.com/macros/s/AKfycbwaqlj_kBAn9LLav0qv6GmXlWk-hwIosHA- 1_1YoMutiiuGy84/exec?order_number=1451875765851&delivered=true

To handle this query, the doGet function should be updated again as follows:

function doGet(e){
  var delivered = e.parameter.delivered;
  
  if(delivered){
    // If order delivered then just update delivery date.
    updateDelivery(e);
    
    // Returning text content is enough, HtmlService not needed.
    return ContentService.createTextOutput("Thank you!");
  }
  
  var orderNumber = e.parameter.order_number;

  if(orderNumber){
    
    /*
     *  If order number present in query string
     *  then serve dispatch form to order processing unit.
     *
     */
    var template = HtmlService.createTemplateFromFile(...