add some TLS options to kafka.json

[nwt]

New options:

• tls_client_cert_file
• tls_client_key_file
• tls_server_ca_cert_file
• tls_server_insecure_skip_verify

[philrz]

This tested out nicely for me. I put together a Gist that walks through the steps I took in validating it:

https://gist.github.com/philrz/f0e926e04debb332f81d554163464e13

Once this merges and we cut another release I'd be game to put up a PR to have this guide added to the repo. Even if few users have reason to walk through it, I know I don't trust my own memory to recall all the steps to getting back to working configs again should I need to help someone troubleshoot in the future, so it'd be helpful to have around even if just for my own future reference.

I'll check with the target user to confirm if they're ok doing their own testing based on the branch/Gist so we can confirm it meets their needs before we create a release.

[philrz]

The target user repots they've done their own testing and are satisfied with the functionality, so we're clear to merge and create a release.