refactor(install): Get reference for Users group via Enum

[refack]

Description

1. Update function description to reflect current logic
2. Get the reference to the well-known Users Group by using the WellKnown enum, instead of a magic string.

Motivation and Context

Make intended object name strongly typed and explicitly named.
Should be easier for humans to read and understand

How Has This Been Tested?

1. Step debugger confirms the resulting object is identical.
2. Current test suit has not regressed.

Checklist:

• I have read the Contributing Guide.
• I have ensured that I am targeting the develop branch.
• [] I have updated the documentation accordingly.
• [] I have updated the tests accordingly.
• I have added an entry in the CHANGELOG.

[refack]

Hello all

I'm dipping my toe in the codebase and thought this might be a nice and small first PR.
Do I need to add a line in the changelog for this?