Certificate authentication to warpgate

[rafabr]

We have a bunch of old network devices that we want to be accessible only through warpgate. We also use ansible to deploy config changes in batch.

It would be nice to be able to authenticate to warpgate using certificate authentication. In this way, we could use 2FA only once to get our public key signed with a short TTL (using Vault, for example) and use it to apply config changes to all devices via ansible.

Enabling this feature in openSSH is as easy as adding the TrustedUserCAKeys option pointing to a CA public key.

I think that it would be a worthy addition.