gas_get_cookie

//Получаем cookie, отправляя логин и пароль

function getDoggyLogsCookie() {
  let url = 'https://doggylogs.com/login/authenticate'
  let params = {
    method: "POST",
    'contentType': 'application/x-www-form-urlencoded',
    "followRedirects": false,
    'payload': {
      'username': '123', 'password': '456'
    }
  };

  let resp = UrlFetchApp.fetch(url, params)
  let headers = resp.getAllHeaders();
  let cookies = headers['Set-Cookie'].split(';')[0];

  Logger.log(cookies);
  return cookies;
}