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, 0 deletions

diff --git a/spec/factories/users.rb b/spec/factories/users.rb
index 58602c54c7a..249dabbaae8 100644
--- a/spec/factories/users.rb
+++ b/spec/factories/users.rb
@@ -28,6 +28,7 @@ FactoryGirl.define do
 
     trait :ghost do
       ghost true
+      after(:build) { |user, _| user.block! }
     end
 
     trait :two_factor_via_otp do