How to automate SSL certificate to page builder site?

You've received recommendations for LetsEncrypt and Certbot, but it doesn't look like you've followed up either of them. Certbot is a script that will automatically create LetsEncrypt certificates and install them directly into the nginx server instances, basically doing all the heavy lifting of the automation you need to do. LetsEncrypt is, of course, a certificate authority, so you're not dealing with self-signed certificates. I strongly recommend looking into Certbot for your application.

See: certbot

You can even load it as a Python module under pyenv and/or virtualenv for kicks.