Add config setting auth_methods

[straight-shoota]

This adds a auth_methods config setting which allows to configure which auth methods the client should accept.

The settings value is a list of comma separated values. The default is scram-sha-256,md5. cleartext needs to be explicitly enabled.

Is there any place where documentation can be added?

I didn't do anything about OK authentication frame. A safe default should also fail if the server just passes you through without a credential check.
But this is more complicated because it is fine with SSL client certificate for example.
So it needs more work. For now I'm just posting this patch.

Superseeds #218
cf crystal-lang/crystal-db#141

[will]

Overall this is good, and meets what I was looking for in having cleartext be opt-in. Thank you

Is there any place where documentation can be added?

The only place right now is the ever growing and not well organized readme. I suppose we should eventually build some better doc thing sooner or later.

anything about OK authentication frame.

Yeah this is a little more complex. For the reason you say and also, if I remember correctly, if you're connecting over like a local unix socket, and pg is doing ident/peer auth, you just get OK and that is legitimately ok. I think we can probably leave this one be for now, but we can wait a bit to see if there are any counter examples.

But again, overall looks good :) Let me know when you think it's ready ready.

[straight-shoota]

I think this is ready to merge. As you said, further improvements can follow later.

[will]

I think this is ready to merge. As you said, further improvements can follow later.

Sounds good, I'll do this tomorrow.

[will]

Thank you! Going to wrap up a few other things then do a release soon.