pundit: convert artists to pundit.

app/policies/artist_policy.rb

@@ -0,0 +1,21 @@
+class ArtistPolicy < ApplicationPolicy
+  def ban?
+    user.is_admin? && !record.is_banned?
+  end
+
+  def unban?
+    user.is_admin? && record.is_banned?
+  end
+
+  def revert?
+    unbanned?
+  end
+
+  def permitted_attributes
+    [:name, :other_names, :other_names_string, :group_name, :url_string, :is_deleted, { wiki_page_attributes: [:id, :body] }]
+  end
+
+  def permitted_attributes_for_new
+    permitted_attributes + [:source]
+  end
+end