Cannot view admin form on D11

The changes made to the admin form in the issue fork allow it to load successfully for me.

This patch does seem to fix the D11 compatability by addressing https://www.drupal.org/node/3404140 → and https://www.drupal.org/node/3349759 → . The fixes look to be backwards compatible for D10 as well.

A few items possibly worth addressing:

These changes introduce some code standards/formatting violations.

1. Inline comments
2. Lost a docblock (::create method)
3. Whitespace added after a method’s closing bracket

Also, although calling Role::loadMultiple is noted in the change record where user_role_names() is deprecated, it’d be a more-appropriate solution to obtain the entity type manager service via dependency injection rather than calling the static method on the entity class.

One last thought, the constructor could be updated to use constructor property promotion, which is a cleaner solution versus the “normal” class properties and setter code in the constructor. We'll be seeing this more throughout core and contrib in the future.

Implemented changes as noted in #4 🐛 Cannot view admin form on D11 Active except the constructor property construction, which I decided against as it does seem to be used elsewhere in the module.