Supporting client authentication

[MichaelViveros]

Hello, I'm adding client authentication to my application and I want to use stubbex to test it. To support this, I think all we would need to do is add some SSL configs similar to stubbex_cert_pem that would allow the client to send its client certificate and the server to verify it. Let me know what you think and I can get started on a PR if you're on board.

[MichaelViveros]

@yawaramin ?

[yawaramin]

Hi Michael, am I understanding correctly that this change would allow Stubbex to talk to an HTTPS endpoint on behalf of a client application? If so, sure, that sounds good to me!

[MichaelViveros]

Doesn't Stubbex already support that? I just want to extend it so instead of only supporting server certificate verification for https endpoints it will also support client certificate verification (as part of Mutual TLS). Wiremock supports this - http://wiremock.org/docs/https/, Requiring client certificates