call a webhook on opening Google doc

onOpen.gs

// https://developers.google.com/apps-script/guides/triggers
function onOpen() {
  var webhookUrl = 'https://X.X.X.X/';

  var payload = {
    'action': 'Open',
    'timestamp': new Date().toISOString(),
    'userInfo': Session.getActiveUser().getEmail()
      };
  var options = {
    'method': 'post',
    'contentType': 'application/json',
    'payload': JSON.stringify(payload)
  };
  UrlFetchApp.fetch(webhookUrl, options);
}