[FEATURE] Add describeSoap feature for contributors

[JoernBerkefeld]

official docs (useless): https://developer.salesforce.com/docs/marketing/marketing-cloud/guide/describe.html

community docs: https://salesforce.stackexchange.com/a/350156

sample callout:

<?xml version="1.0" encoding="UTF-8"?>
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
    <s:Header>
        <a:Action s:mustUnderstand="1">Describe</a:Action>
        <a:To s:mustUnderstand="1">https://{{et_subdomain}}.soap.marketingcloudapis.com/Service.asmx</a:To>
        <fueloauth xmlns="http://exacttarget.com">{{dne_etAccessToken}}</fueloauth>
    </s:Header>
    <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
        <DefinitionRequestMsg xmlns="http://exacttarget.com/wsdl/partnerAPI">
         <DescribeRequests>
            <ObjectDefinitionRequest>
               <ObjectType>ImportDefinition</ObjectType>
            </ObjectDefinitionRequest>
         </DescribeRequests>
      </DefinitionRequestMsg>
    </s:Body>
</s:Envelope>

[github-actions[bot]]

Closed by #1465.