WSO2 BPS: How to pass Header values as a part of a Message in BPEL Invoke - bpel

Question

My web service operation is defined like below. Where I have a header parameter as well.
public void method(#WebParam(name="OrderNo", mode=WebParam.Mode.IN) String order_no_,
#WebParam(name="user", mode=WebParam.Mode.IN, header=true) String user)
Now when I deploy this service I get a WSDL which looks like this.
<?xml version="1.0" ?>
<wsdl:definitions ... >
<wsdl:types>
</xs:schema>
...
<xs:element name="method" type="tns:method"></xs:element>
<xs:complexType name="method">
<xs:sequence>
<xs:element minOccurs="0" name="OrderNo" type="xs:string"></xs:element>
</xs:sequence>
</xs:complexType>
...
<xs:element name="user" nillable="true" type="xs:string"></xs:element>
...
</xs:schema>
</wsdl:types>
...
<wsdl:message name="method">
<wsdl:part element="tns:method" name="parameters" />
<wsdl:part element="tns:user" name="user" />
</wsdl:message>
...
<wsdl:portType name="CustomerOrderService">
<wsdl:operation name="method">
<wsdl:input message="tns:method" name="method" />
<wsdl:output ... />
<wsdl:fault ... />
</wsdl:operation>
</wsdl:portType>
...
<wsdl:binding name="OrderSoapBinding" type="tns:OrderService">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />
<wsdl:operation name="method">
<soap:operation soapAction="" style="document" />
<wsdl:input name="method">
<soap:header message="tns:method" part="user" use="literal" />
<soap:body parts="parameters" use="literal" />
</wsdl:input>
<wsdl:output name="...">
<soap:body use="literal" />
</wsdl:output>
<wsdl:fault name="...">
...
</wsdl:fault>
</wsdl:operation>
</wsdl:binding>
</wsdl:definitions>
As you can see the header is part of the message used as input for the service request. Hwen I use soap UI to test this WSDL it generated a proper soap message with the "user" property as part of the header.
When I use this service as a partner link in a Carbon BPEL process, and assign a value to the "user" part in the invoke message, the value is not included in the header.
<bpel:variable name="method_Input" messageType="ns0:method" />
<bpel:assign name="...">
...
<bpel:copy>
<bpel:from>$input.payload/tns:TaskReceiver</bpel:from>
<bpel:to>$method_Input.user</bpel:to>
</bpel:copy>
</bpel:assign>
You can see that the message part is assigned the proper value,
The problem is this message part which is bound to the header of of the soap message is never included in the soap header.
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Body>
<method xmlns="http://customerorder.service.test/">
<OrderNo xmlns="">ORD00011</OrderNo>
</method>
</soapenv:Body>
</soapenv:Envelope>
Thanks in advance to any help provided.