Adds release group urls

lib/musicbrainz/bindings/release_group.rb

@@ -8,7 +8,10 @@ module MusicBrainz
           type: (xml.attribute('type').value rescue nil),
           title: (xml.xpath('./title').text rescue nil),
           desc: (xml.xpath('./disambiguation').text rescue nil),
-          first_release_date: (xml.xpath('./first-release-date').text rescue nil)
+          first_release_date: (xml.xpath('./first-release-date').text rescue nil),
+          urls: (Hash[xml.xpath('./relation-list[@target-type="url"]/relation').map{ |xml|
+            [xml.attribute('type').value.downcase.split(" ").join("_").to_sym, xml.xpath('./target').text]
+          }] rescue {})
         }
       end
 

lib/musicbrainz/models/artist.rb

@@ -9,7 +9,7 @@ module MusicBrainz
     field :urls, Hash
 
     def release_groups
-      @release_groups ||= client.load(:release_group, { artist: id }, {
+      @release_groups ||= client.load(:release_group, { artist: id, inc: [:url_rels] }, {
         binding: :artist_release_groups,
         create_models: :release_group,
         sort: :first_release_date

lib/musicbrainz/models/release_group.rb

@@ -5,6 +5,7 @@ module MusicBrainz
     field :title, String
     field :desc, String
     field :first_release_date, Date
+    field :urls, Hash
 
     alias_method :disambiguation, :desc
 
@@ -18,7 +19,7 @@ module MusicBrainz
 
     class << self
       def find(id)
-        client.load(:release_group, { id: id }, {
+        client.load(:release_group, { id: id, inc: [:url_rels] }, {
           binding: :release_group,
           create_model: :release_group
         })