Add support for mutual tls configuration

[joshiste]

Adds support to configure the parameters needed for mutual tls (see https://www.keycloak.org/server/enabletls#_enabling_mutual_tls)

[dasniko]

Thanks for providing this. I made some comments to your code, please have a look at it. 🙂

[joshiste]

@dasniko sorry, but I can't find your comments on this PR. Where did you left 'em?

[dasniko]

Sorry, my fault. Didn't finish the review properly.

[joshiste]

@dasniko PR updated.