add working (though no-op) PostModerationRecordPolicy

Author: timdiggins

app/controllers/thredded/moderation_controller.rb

@@ -21,6 +21,7 @@ def history
         .send(Kaminari.config.page_method_name, current_page)
         .preload(:messageboard, :post_user, :moderator, post: :postable)
         .preload_first_topic_post
+      authorize @post_moderation_records
     end
 
     def activity

app/policies/thredded/post_moderation_record_policy.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module Thredded
+  class PostModerationRecordPolicy
+    def initialize(user, scope)
+      @user = user
+      @scope = scope
+    end
+
+    def history?
+      true
+    end
+  end
+end