This will allow consumers to inject it using `currentUser: service()` in preparation for the removal of implicit injections in Ember 4.0. `current-user:main` is still available and will print a deprecation notice.
* Use QUnit `module` instead of `discourseModule`
* Use QUnit `test` instead of `componentTest`
* Use angle-bracket syntax
* Remove jQuery usage
* Improve assertions (and actually fix some of them)