Fix PostgreSQL major version upgrade restriction in CloudFormation

[jfrench9]

Summary

This PR resolves a configuration issue in the PostgreSQL CloudFormation template that was preventing major version upgrades of RDS instances.

Key Changes

• Added the AllowMajorVersionUpgrade parameter to the PostgreSQL RDS configuration
• Enables controlled major version upgrades for PostgreSQL databases when needed

Accomplishments

• ✅ Removes upgrade restriction that could block critical security updates
• ✅ Provides flexibility for planned database version migrations
• ✅ Maintains backward compatibility with existing deployments

Breaking Changes

None. This change only adds capability and does not modify existing behavior for current deployments.

Testing Notes

• Verify that existing PostgreSQL instances remain unaffected
• Test that major version upgrades can now be performed when the parameter is explicitly set
• Confirm that the default behavior (no automatic upgrades) is preserved

Infrastructure Considerations

• This change affects RDS PostgreSQL instances managed by CloudFormation
• Major version upgrades should still be planned and tested in non-production environments first
• Consider database compatibility requirements before initiating major version upgrades
• Monitor applications for any compatibility issues after version upgrades

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🤖 Generated with Claude Code

Branch Info:

• Source: bugfix/rds-pg-update-major-flag
• Target: main
• Type: bugfix

Co-Authored-By: Claude noreply@anthropic.com

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