It is not at all straightforward to figure out how to actually use Kerberos with Ruby driver. In particular there need to be system packages installed for auth to work which neither driver nor server directly depend on.

If we expect users to actually use Kerberos we need to provide guidance on how to make it work.

The documentation should be aligned with server documentation for enabling Kerberos support on the server side.

The documentation should most likely go into driver tutorial, similarly to how driver tutorial links to/includes bson documentation.