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.
Not only is the current code not needed but it's also creating invalid values on safari if the header goes out of viewport with negative values.
This commit also adds a missing test for `--header-offset` property.
* 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)
* FIX: Restore dismissing the first notification
Reverts the temporary fix (8e4fea897e) and restores the feature introduced in e638d43f0a.
The issue that was the reason for the revert (https://meta.discourse.org/t/logins-redirects-to-missing-notifications-page/149718) was a combination of two bugs:
1. Fixed in this commit - the click listener was accidentally registered also for logged-out users. This meant that the first click on a page always trigger an AJAX call to the notifications endpoint (`/notifications?recent=true&limit=5`), which returned a 403 error. Now, this code is run only when the user is logged in.
2. A still unknown bug that I could not reproduce, which was somehow setting the login redirect cookie to the URL of that previously failed AJAX request.
