- Create an internal certificate for the proxy host
- Add internal certificate to proxy host, implement redirection (if necessary)
- Add proxy host to Reverse Proxy
- Request LetsEncrpt External Certificate
- proxy_ssl_trusted_certificate
https://www.supereasy.com/how-to-configure-nginx-as-a-https-reverse-proxy-easily/
https://docs.nginx.com/nginx/admin-guide/security-controls/securing-http-traffic-upstream/