fix(pg-db): use scram-sha-256 auth instead of md5 for PostgreSQL

[nogueiraanderson]

Summary

• PostgreSQL 14+ defaults to password_encryption=scram-sha-256
• pg_hba rules specified md5 authentication
• MD5 auth cannot verify SCRAM-SHA-256 stored passwords
• Changed pg_hba rules from md5 to scram-sha-256

Root Cause

Authentication failures for pmmuser and gfuser:

pq: password authentication failed for user "pmmuser"

The passwords matched in both secrets (pmm-secret and pmmuser-credentials), but authentication still failed because:

• PostgreSQL stored passwords as SCRAM-SHA-256
• pg_hba.conf specified md5 authentication method

Testing

Verified fix on live ROSA HCP cluster - PMM pods became Ready after patching Patroni config.

[it-percona-cla]

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