Creating "Headers" object in Google Apps Script for API call

Question

I am looking to pull data from Thinkific's API into a Google sheet, but unfortunately I am not able to create a working API request in Apps Script.

I have built the request in Postman and tried to just reuse the javascript code in Apps Script, but get the error that "Headers is not defined". The function Headers() to create the headers object just doesn't seem to exist for Apps Script. Any way to manually create the headers object and then append the API key as well as the subdomain for authentication?

function myFunction() {

var myHeaders = new Headers();
myHeaders.append("X-Auth-Subdomain", "xyz");
myHeaders.append("X-Auth-API-key", "xyz");

var requestOptions = {
  method: 'GET',
  headers: myHeaders,
  redirect: 'follow'
};

fetch("https://api.thinkific.com/api/public/v1/orders?page=1&limit=25", requestOptions)
  .then(response => response.text())
  .then(result => console.log(result))
  .catch(error => console.log('error', error));
  
}

Thanks a lot!