Backend authentication is not bypassed correctly for SCRAM

[b1ron]

FerretDB version

v1.20.0-12-gb6fd73b4-dirty

Backend

PostgreSQL

Environment

dev

What did you do?

See repro #4119.

What did you expect to see?

A successful connection.

What did you see instead?

MongoServerError: [msg_saslstart.go:184 handler.(*Handler).scramCredentialLookup] [collection.go:57 postgresql.(*collection).Query] [registry.go:279 metadata.(*Registry).DatabaseGetExisting] [registry.go:132 metadata.(*Registry).getPool] [pool.go:128 pool.(*Pool).Get] [opendb.go:95 pool.openDB] [opendb.go:110 pool.checkConnection] failed to connect to `host=127.0.0.1 user=byron database=ferretdb`: failed SASL auth (FATAL: password authentication failed for user "byron" (SQLSTATE 28P01))

[AlekSi]

Let's re-check with the current dev version

[b1ron]

This is no longer an issue with the current version. However, what's quite confusing is that is passes locally but only once, and always fails on CI. It could be related to the fact that we authenticate using a new client instance in the shell.

I need to debug the test further in #4119 to fully understand the problem.