feat: use scram hash in users.toml

[levkk]

Allow to specify SCRAM-SHA-256 hashes in users.toml instead of plaintext passwords. Users can authenticate to pgdog without us having to store the password anywhere.

Server auth has to be passwordless, however, e.g. RDS IAM or trust.

[codecov]

Codecov Report

❌ Patch coverage is 73.05389% with 45 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog-config/src/users.rs	57.57%	14 Missing ⚠️
pgdog/src/backend/pool/connection/mod.rs	0.00%	11 Missing ⚠️
pgdog/src/auth/scram/server.rs	90.00%	9 Missing ⚠️
pgdog/src/cli.rs	0.00%	7 Missing ⚠️
pgdog/src/frontend/client/mod.rs	0.00%	4 Missing ⚠️

📢 Thoughts on this report? Let us know!

[blacksmith-sh]

Found 2 test failures on Blacksmith runners:

Failures

Test	View Logs
unbans all pools	View Logs
connection/tcp broken database both down unbans all pools	View Logs