internal: type improvements

[mshima]

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Please make sure the below checklist is followed for Pull Requests.

• [ ] All continuous integration tests are green
• [ ] Tests are added where necessary
• [ ] The JDL part is updated if necessary
• [ ] jhipster-online is updated if necessary
• [ ] Documentation is added/updated where necessary
• [ ] Coding Rules & Commit Guidelines as per our CONTRIBUTING.md document are followed

When you are still working on the PR, consider converting it to Draft (below reviewers) and adding skip-ci label, you can still see CI build result at your branch.