=== Goal
#anti-harassment Tools team is redesigning CheckUser to support an easier and faster workflow to retrieve CheckUser information. In order to avoid disruption to existing CheckUser processes while we work on this, we should setup a new Special page which will work as our test environment. This will allow us to iterate quickly and share our progress with the users.
=== Acceptance criteria:
* There is a new blank/hello-world special page created by the CheckUser extension, titled //Special:Investigate// behind a feature flag
* The special page is only enabled on testwiki
* If config is set to unavailable, the special page URL points to a page with the title "No such special page" (similar to Special:Mute)
* If config is set to available:
** Unblocked user with `checkuser` right sees the page title and a submit button that does nothing
** Blocked user with `checkuser` right sees a user blocked error (similar to Special:CheckUser)
** User with `checkuser` right sees the special page listed at Special:SpecialPages under the section "Users and rights" (similar to Special:CheckUser)
** User without `checkuser` right sees a permissions error