Delete playlist items via content owner (#375)

* Delete playlist items via content owner

* Add default to params[:params]

lib/yt/models/account.rb

@@ -192,6 +192,10 @@ def video_groups_params
         {mine: true}
       end
 
+      def playlist_items_params
+        {}
+      end
+
       # @private
       # Tells `has_many :resumable_sessions` what path to hit to upload a file.
       def upload_path

lib/yt/models/content_owner.rb

@@ -102,6 +102,10 @@ def upload_params
       def video_groups_params
         {on_behalf_of_content_owner: @owner_name}
       end
+
+      def playlist_items_params
+        {on_behalf_of_content_owner: @owner_name}
+      end
     end
   end
 end

lib/yt/models/playlist_item.rb

@@ -101,6 +101,13 @@ def resource_id
         {kind: 'youtube#video', videoId: video_id}
       end
 
+      def delete_params
+        super.tap do |params|
+          params[:params] ||= {}
+          params[:params].merge! @auth.playlist_items_params
+        end
+      end
+
       # @see https://developers.google.com/youtube/v3/docs/playlistItems/update
       def update_parts
         keys = [:position, :playlist_id, :resource_id]
@@ -109,4 +116,4 @@ def update_parts
       end
     end
   end
-end
+end