batch purchase loading

ruby/lib/jam_ruby/models/jam_track.rb

@@ -257,7 +257,7 @@ module JamRuby
 
       def purchases_metadata(user)
         JamTrack.
-          select(['jam_tracks.id', :name, :original_artist, :year]).
+          select(['jam_tracks.id', :name, :original_artist, :year, 'jam_track_rights.created_at AS purchased_at']).
           joins(:jam_track_rights).
           where("jam_track_rights.user_id = ?", user.id).
           includes(:genres).

web/app/views/api_jam_tracks/show_for_mobile.rabl

@@ -1,3 +1,7 @@
 object @jam_track
 
 attributes :id, :name, :original_artist, :year, :genre_name
+
+node :purchased_at do |jt|
+ Time.parse(jt.purchased_at).to_i rescue Time.now
+end