feat: identify the source of auth for new server connections

[levkk]

new server connection: auth=trust, source=rds iam, reason=min [pgdog@localhost:5432/shard_1]

[codecov]

Codecov Report

❌ Patch coverage is 80.95238% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/backend/pool/password.rs	86.66%	2 Missing ⚠️
pgdog/src/backend/server.rs	50.00%	2 Missing ⚠️

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[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
lb_tests/TestReloadWithAutoRole	View Logs