def prepare_recipients_data_from sparkpost_data
      if (recipients_data = sparkpost_data[:recipients])
        @data[:recipients].each_with_index do |recipient, index|
          if (recipient_data = recipients_data[index])
            recipient.merge!(recipient_data)
          end
        end
      end
    end
def prepare_recipients_data_from sparkpost_data
      if (recipients_data = sparkpost_data[:recipients])
        @data[:recipients].each_with_index do |recipient, index|
          if (recipient_data = recipients_data[index])
            recipient.merge!(recipient_data)
          end
        end
      end
    end
See https://developers.sparkpost.com/api/#/introduction/substitutions-reference/links-and-substitution-expressions-within-substitution-values