Add moderator role and add pundit policies for admin actions (#5635)

* Add moderator role and add pundit policies for admin actions

* Add rake task for turning user into mod and revoking it again

* Fix handling of unauthorized exception

* Deliver new report e-mails to staff, not just admins

* Add promote/demote to admin UI, hide some actions conditionally

* Fix unused i18n

app/policies/account_moderation_note_policy.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class AccountModerationNotePolicy < ApplicationPolicy
+  def create?
+    staff?
+  end
+
+  def destroy?
+    admin? || owner?
+  end
+
+  private
+
+  def owner?
+    record.account_id == current_account&.id
+  end
+end