How To Preserve SOAP Headers to use with Mule 4 Web Service Consumer?

Question

I have used an Existing WSDL to create an Experience API where I am performing several steps before either:

1. Passing the SOAP Request Message as-is to the Original Backend System using Mule4 Web Service Consumer or
2. Calling another Backend System (RESTful API) and transforming the Response to match the Expected SOAP Response Message

Sample Message

<env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope" xmlns:ns="urn:Acme/PublicService/V1" xmlns:ns0="urn:/Acme/BasicDataPublicService/V1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <env:Header>
        <a:Action s:mustUnderstand="1" xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:s="http://www.w3.org/2003/05/soap-envelope">urn:Acme/PublicService/V1/PublicService/SetCustomer</a:Action>
        <a:MessageID xmlns:a="http://www.w3.org/2005/08/addressing">urn:uuid:4afe0693-adea-4ede-bec9-10b694708d85</a:MessageID>
        <a:ReplyTo xmlns:a="http://www.w3.org/2005/08/addressing">
            <a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
        </a:ReplyTo>
        <VsDebuggerCausalityData xmlns="http://schemas.microsoft.com/vstudio/diagnostics/servicemodelsink">uIDPo8KxyyGpakdIj8o84JOeAMsAAAAAQBkt3vfAK0C4dDgn3rAKx/iXgqYosnhKv/OHgph9cXoACQAA</VsDebuggerCausalityData>
        <a:To s:mustUnderstand="1" xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:s="http://www.w3.org/2003/05/soap-envelope">http://316.820.517.311:36990/PublicInterface/Service</a:To>
        <AuthorizationToken xmlns="urn:Acme/Authorization/V1" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
            <CultureName>uk-UK</CultureName>
            <OnBehalfOf i:nil="true"></OnBehalfOf>
            <Password>****</Password>
            <UserName>sa-ACME</UserName>
        </AuthorizationToken>
    </env:Header>
    <env:Body>
        <ns:SetCustomer>Muli-Tier Message</ns:SetCustomer>
    </env:Body>
</env:Envelope>

According to Mulesoft KB; this requires additional Transformation steps in the beginning of the flow. Passing the SOAP Body is not an issue; the SOAP Header is a pickle, however. Especially since the KB document is hard-coding the values; while in my case these need to be dynamic (i.e. coming from the Original SOAP Request message).

I tried mapping the Header Parameters to a Variable as described but I cannot seem to get to it.

Option 1 Mapping the Header Elements to Children Attributes of a Variable, results in the Variable Storing Null

%dw 2.0
output application/xml writeDeclaration=false, writeNilOnNull=true
ns ns0 http://www.w3.org/2005/08/addressing
ns s http://www.w3.org/2003/05/soap-envelope
---
headers: {
    ns0#Action @(s#mustUnderstands: payload.headers.Action.@mustUnderstands): payload.headers.Action as String default null,
    ns0#MessageID: payload.headers.MessageID as String default null,
    ns0#ReplyTo: {
        ns0#Address: payload.headers.ReplyTo.Address as String default null
    },
    VsDebuggerCausalityData: payload.headers.VsDebuggerCausalityData as String default null,
    ns0#To @(s#mustUnderstands: payload.headers.To.@mustUnderstands): payload.headers.To as String default null,
    AuthorizationToken: {
        CultureName: payload.headers.AuthorizationToken.CultureName as String default null,
        OnBehalfOf: payload.headers.AuthorizationToken.OnBehalfOf as String default null,
        Password: payload.headers.AuthorizationToken.Password as String default null,
        UserName: payload.headers.AuthorizationToken.UserName as String default null
    }
}

Option 2 Mapping payload.headers to a Variable, results in extra tags; and losing the XML Tag attributes

%dw 2.0
output application/xml writeDeclaration=false, writeNilOnNull=true
ns ns0 http://www.w3.org/2005/08/addressing
ns s http://www.w3.org/2003/05/soap-envelope
---
headers: payload.headers

Answer 1

I will come back and add more details on the answer, but here is how to solve that issue:

%dw 2.0
output application/xml writeDeclaration=false, writeNilOnNull=true
---
headers: (payload.headers.headers mapObject (value, key) -> {
(value)
})