rename context to serialization_context and add url helpers

lib/active_model/serializer/railtie.rb

@@ -7,6 +7,18 @@ module ActiveModel
       end
     end
 
+    initializer 'active_model_serializers.url_helpers' do
+      ActiveSupport.on_load(:action_controller) do
+        ActiveModelSerializers.url_helpers = Module.new do
+          include Rails.application.routes.url_helpers
+
+          def self.default_url_options
+            ActionController::Base.default_url_options
+          end
+        end
+      end
+    end
+
     initializer 'generators' do |app|
       app.load_generators
       require 'generators/serializer/resource_override'