def enter_offline_payment(attrs={})
      Transaction.from_response API.post("#{uri}/transactions", attrs.empty? ? nil : Transaction.to_xml(attrs))
    rescue Recurly::API::UnprocessableEntity => e
      raise Invalid, e.message
    end
def enter_offline_payment(attrs={})
      Transaction.from_response API.post("#{uri}/transactions", attrs.empty? ? nil : Transaction.to_xml(attrs))
    rescue Recurly::API::UnprocessableEntity => e
      raise Invalid, e.message
    end
Posts an offline payment on this invoice

 @return [Transaction]
 @raise [Error] If the transaction fails.