[DPE-6902] Replace md5 with scram-sha-256 in patroni/pg_hba.conf

[taurus-forever]

Issue

We have migrated from md5 to scram-sha-256 but still falling back to md5 in pg_hba.conf

Solution

Complete migration to scram-sha-256.
Support instance_password_encryption charm config option.

Checklist

• I have added or updated any relevant documentation.
• I have cleaned any remaining cloud resources from my accounts.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.87%. Comparing base (a42d4db) to head (32b6c26).
⚠️ Report is 70 commits behind head on 16/edge.

Additional details and impacted files

@@           Coverage Diff            @@
##           16/edge    #1004   +/-   ##
========================================
  Coverage    64.87%   64.87%           
========================================
  Files           17       17           
  Lines         4270     4270           
  Branches       656      656           
========================================
  Hits          2770     2770           
  Misses        1333     1333           
  Partials       167      167           

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[taurus-forever]

PG<>PGB<>APP test passed, but IMHO, the code can be simplified here.

[dragomirp]

We should reconsider the instance_password_encryption config as a follow up. Setting it to md5 will not be practically usable, since users won't be able to login with md5 pass hashes.

[taurus-forever]

We should reconsider the instance_password_encryption config as a follow up. Setting it to md5 will not be practically usable, since users won't be able to login with md5 pass hashes.

Good point. Should I include it into this PR? @dragomirp

[taurus-forever]

Requested review once again after adding instance_password_encryption config option.