Don't allow deleting a ghost user.

- Add a `destroy_user` ability. This didn't exist before, and was implicit in
  other abilities (only admins could access the admin area, so only they could
  destroy all users; a user can only access their own account page, and so can
  destroy only themselves).

- Grant this ability to admins, and when the current user is trying to destroy
  themselves. Disallow destroying ghost users in all cases.

- Modify the `Users::DestroyService` to check this ability. Also check it in
  views to decide whether or not to show the "Delete User" button.

- Add a short summary of the Ghost User to the bio.

1 files changed, 1 insertions, 1 deletions

diff --git a/app/services/users/destroy_service.rb b/app/services/users/destroy_service.rb
index 523279944ae..833da5bc5d1 100644
--- a/app/services/users/destroy_service.rb
+++ b/app/services/users/destroy_service.rb
@@ -7,7 +7,7 @@ module Users
     end
 
     def execute(user, options = {})
-      unless current_user.admin? || current_user == user
+      unless Ability.allowed?(current_user, :destroy_user, user)
         raise Gitlab::Access::AccessDeniedError, "#{current_user} tried to destroy user #{user}!"
       end