added PinnedLink#timed? for checking if a featured link is time-constrained

Author: Oaphi

app/models/pinned_link.rb

@@ -1,4 +1,10 @@
 class PinnedLink < ApplicationRecord
   include MaybeCommunityRelated
   belongs_to :post
+
+  # Is the link time-constrained?
+  # @return [Boolean] check result
+  def timed?
+    shown_before.present? || shown_after.present?
+  end
 end