Refactory the entity id

Summary

Introduces a wrapper class for the EntityID. This is a prerequisite for the refactoring of the file system and this will also make it easier to implement string-ids in the future.

Focus

• Most of the changes are something like

  -Integer
  +EntityID

• an automated formatter/linter added a few finals here and there.

  
  +final

• Entity is an abstract class now. Instead, we use RetrieveEntity, UpdateEntity,... etc. whenever we use and entity. This gives some clarity when we want to know, what will happen with an entity.
• Some other unrelated refactoring happened in various places

Test Environment

The dev pipelines must run through just fine, because this does not change the API, just the implementation

Check List for the Author

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• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

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