Implements #421 & refactor enum -> literal types

[remojansen]

Description

Implements #421 & refactor enum -> literal types

Related Issue

#421

Motivation and Context

#421

How Has This Been Tested?

Added some extra unit tests

Types 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)

Checklist:

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

[mention-bot]

@remojansen, thanks for your PR! By analyzing the history of the files in this pull request, we identified @endel and @hourliert to be potential reviewers.