Add support for GSS/Kerberos with Postgres 12

[mp911de]

Postgres 12 added Kerberos support, so it would make sense to support it as well. We need to ensure that Kerberos support doesn't introduce blocking calls when obtaining the principal where we don't want to have blocking calls.

Reference:

• Gssapi encrypted pgjdbc#1821
• https://www.postgresql.org/docs/12/gssapi-auth.html

[govi20]

anyone working on this? I would like to give it a shot.

[mp911de]

Feel free, we hadn't had the time yet to work on this ticket.

[davecramer]

Be a bit careful here. When I implemented it on the JDBC driver I tried to see if the server would respond correctly and a few big cloud providers just errored and closed the connection. Currently the driver uses some private methods to see if there is a key cached before attempting a GSS conversation. This is not ideal either

[govi20]

@davecramer Sure, thanks for the inputs. Let me go through the JDBC patch to get an understanding of how it works.