patch: MongoDB 8.0.28 and PBM Agent log file

[Gu1nness]

🏷️ Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tooling and CI
• Dependencies upgrade or change
• Chores / refactoring

📝 Description

• PBM 8.0.28
• PBM Agent log file: Configure PBM Agent with a config file to have it logged into a dedicated file.

🧪 Manual testing steps

1. juju deploy <my-app>
2. …

🔬 Automated testing steps

✅ Checklist

• My code follows the code style of this project.
• I have added or updated any relevant documentation.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.