refund spec

lib/yandex-checkout.rb

@@ -10,6 +10,7 @@ require 'yandex-checkout/response'
 require 'yandex-checkout/callable'
 require 'yandex-checkout/optional'
 require 'yandex-checkout/entity/payment'
+require 'yandex-checkout/entity/refund'
 require 'yandex-checkout/error'
 # require 'yandex-checkout/entity/amount'
 # require 'yandex-checkout/entity/payment_method'