Impl client auth

[forderud]

Client-Cert X-Client-Cert

Python links:

• Starting point: https://stackoverflow.com/questions/19705785/python-3-simple-https-server
• https://docs.python.org/3/library/http.server.html
• https://docs.python.org/3/library/ssl.html

Links:

• Node.js impl: https://medium.com/@sevcsik/authentication-using-https-client-certificates-3c9d270e8326