Minor refactoring to use newer Java features

[StefanSpieker]

Minor refactoring to use newer Java features:

• use record
• make use of enhanced instanceof
• use StandardCharsets instead of deprecated com.google.common.base.Charsets

Testing done

Only unit tests.

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed

[timja]

Thanks!