A rudimentary cors gateway for a docusign app.
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
https://nodejs.org/dist/latest-v12.x/docs/api/https.html
https://nodejs.org/dist/latest-v12.x/docs/api/http.html
edit /etc/hosts
a.example.com 127.0.0.1
b.example.com 127.0.0.1