WIP admin settings role filter for no role assigned

[AlexAndBear]

Description

Related Issue

• Fixes <issue_link>

Motivation and Context

How Has This Been Tested?

• test environment:
• test case 1:
• test case 2:
• ...

Screenshots (if appropriate):

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)
• [ ] Technical debt
• [ ] Tests
• [ ] Documentation
• [ ] Maintenance (e.g. dependency updates or tooling)

Open tasks:

• [ ] ...

[update-docs[bot]]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[AlexAndBear]

Current implementation for https://github.com/owncloud/web/issues/10820 but postponed for now