add to_json support

lib/mobility/plugins/attribute_methods.rb

@@ -25,6 +25,14 @@ module AttributeMethods
             attributes.merge(name.to_s => send(name))
           end)
         end
+
+        private
+
+        define_method :attribute_names_for_serialization do
+          return unless defined?(super)
+
+          super() + names.map(&:to_s)
+        end
       end
 
       # Applies attribute_methods plugin for a given option value.

spec/mobility/plugins/attribute_methods_spec.rb

@@ -38,6 +38,13 @@
     end
   end
 
+  describe "#as_json" do
+    it "adds translated attributes to normal attributes" do
+      expect(backend).to receive(:read).with(Mobility.locale, any_args).and_return('foo').at_least(1)
+      expect(instance.as_json).to eq(untranslated_attributes.merge('title' => 'foo'))
+    end
+  end
+
   describe "#untranslated_attributes" do
     it "returns original value of attributes method" do
       expect(instance.untranslated_attributes).to eq(untranslated_attributes)