Fix SOAP request formation for continues

[kimchanyoung]

Description

The Salesforce Marketing Cloud API has a limitation of returning a max of 2500 records per call. As per their documentation, such requests return results where the more attribute is set to true, after which you should be able to call continue to retrieve the next set of 2500 records. This feature does not work as expected.

References:

1. https://developer.salesforce.com/docs/atlas.en-us.noversion.mc-apis.meta/mc-apis/continuerequest_2500records.htm

2. FuelSDK-Ruby/samples/sample-bounceevent.rb

   Line 29 in 99f2fb0

   getResponse = getBounceEvent.continue

Environment

ruby '2.3.1'
gem 'marketingcloudsdk`, `1.0.0`
gem 'rails', '4.2.7.1`

Steps to reproduce

The reproduction requires a sample SFMC environment with an object (in this case, a DataExtension row) with greater than 2500 records.

require 'marketingcloudsdk'

class SfmcButler
  attr_reader :response
  DATA_EXTENSION_NAME = 'DUMMY_EXTENSION_NAME'.freeze
  DATA_EXTENSION_PROPS = ["PROP_1", "PROP_2"].freeze

  def initialize
    @client = MarketingCloudSDK::Client.new({'client' => { 'id' => ENV['SFMC_CLIENT_ID'], 'secret' => ENV['SFMC_SECRET'] }})
    @dataextensionrow = MarketingCloudSDK::DataExtension::Row.new
    @dataextensionrow.authStub = @client
    @dataextensionrow.Name = DATA_EXTENSION_NAME
    @dataextensionrow.props = DATA_EXTENSION_PROPS
  end

  def get_response
    @response = @dataextensionrow.get
  end

  def get_more_responses
    @response = @response.continue
  end
end

The initial get call runs successfully, forming the following XML and returning the first 2500 results:

<?xml version="1.0" encoding="UTF-8"?>
<env:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tns="http://exacttarget.com/wsdl/partnerAPI" xmlns:env="http://schemas.xmlsoap.org/soap/envelope/">
  <env:Header>
      <HEADER INFO HERE>
  </env:Header>
  <env:Body>
    <tns:RetrieveRequestMsg>
      <tns:RetrieveRequest>
        <tns:ObjectType>DataExtensionObject[DUMMY_EXTENSION_NAME]</tns:ObjectType>
        <tns:Properties>PROP_1</tns:Properties>
        <tns:Properties>PROP_2</tns:Properties>
      </tns:RetrieveRequest>
    </tns:RetrieveRequestMsg>
  </env:Body>
</env:Envelope>

@butler.get_response
> ... # Yields the first 2500 responses as expected
@butler.response.class
> MarketingCloudSDK::SoapResponse
@butler.response.more?
> true
@butler.continue
> ... # Yields an array

Further inspection reveals that continue sends the following XML:

<?xml version="1.0" encoding="UTF-8"?>
  <env:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tns="http://exacttarget.com/wsdl/partnerAPI" xmlns:env="http://schemas.xmlsoap.org/soap/envelope/">
    <env:Header>
      <HEADER INFO HERE>
    </env:Header>
    <env:Body>
      <tns:RetrieveRequestMsg>
        <tns:ContinueRequest><ORIGINAL REQUEST ID HERE></tns:ContinueRequest>
      </tns:RetrieveRequestMsg>
    </env:Body>
  </env:Envelope>

This returns an error -- an XML with an unclear error message: "OverallStatus => Error"

Comparing the continue-generated request XML with the one generated by the getMoreRequests method in the Python SDK reveals that the XML body is malformed. For reference, calling getMoreRequests on a result through the Python SDK sends the following XML

...
<ns1:Body>
  <ns0:RetrieveRequestMsg>
    <ns0:RetrieveRequest>
      <ns0:ObjectType/>
      <ns0:ContinueRequest><ORIGINAL REQUEST ID></ns0:ContinueRequest>
      </ns0:RetrieveRequest>
  </ns0:RetrieveRequestMsg>
</ns1:Body>
...

This change corrects the continue method to perform as expected in the docs.

[kimchanyoung]

Goodness -- this is a duplicate PR
Closing in favor of #39

Should have done my homework 🤒