SASL: add support for GSSAPI mechanism

[stevevls]

Describe the solution you'd like
Once #223 is merged, we can add support for GSSAPI (Kerberos) authentication.

Supporting documentation
https://cwiki.apache.org/confluence/display/KAFKA/KIP-43%3A+Kafka+SASL+enhancements
https://docs.confluent.io/current/kafka/authentication_sasl/authentication_sasl_gssapi.html

[psilvaro]

Is there any news about having the support for GSSAPI?
Thanks

[stevevls]

No movement as of yet. If you're interested in taking a stab at it, I think it's a matter of:

1. Adding a kerberos server to the docker compose setup
2. Configuring the kafka container to add another listener that connects to the kerberos server
3. Implementing the sasl.Mechanism. There are examples in sasl/plain and sasl/scram that could serve as a jumping off point.

This isn't currently a critical feature for Segment, so it's one of those when we get around to it sorts of things. We're happy to accept PRs, though! 😄

[achille-roussel]

Just leaving an update that we are still looking into this issue.