feat: SASL client support

[rkrishn7]

Is your feature request related to a problem? Please describe.

Currently, there is no client support for SASL authentication when connecting to the proxy

Describe the solution you'd like

Add SASL authentication as a configurable strategy. The default authentication mechanism will remain md5.

This will likely involve refactoring the authentication logic, possibly into a separate module.

[rkrishn7]

I'm happy to work on this!

[WagnerPMC]

Is your feature request related to a problem? Please describe.

Currently, there is no client support for SASL authentication when connecting to the proxy

Describe the solution you'd like

Add SASL authentication as a configurable strategy. The default authentication mechanism will remain md5.

This will likely involve refactoring the authentication logic, possibly into a separate module.

I've been doing this for the last two weeks. I don't have a lot of time, but I've already made a lot of progress.
I plan to rewrite almost entirely SCRAM authentication as it is now, and add client-server SCRAM authentication.
I think by the end of the month I'll have a result and as a consequence a Pull Request.

p.s. I'm not a PGCat contributor, so PR decisions are out of my hands.