How to create SOAP nested headers with SAVON

Question

I would like to generate following soap header with SAVON but cannot really find any proper documentation for it any help would be appreciated.

<SOAP-ENV:Header>
     <trp:protocolVersion>4.0</trp:protocolVersion>
     <trp:id>*******</trp:id>
     <trp:userId>*******</trp:userId>
     <trp:service crv:objectType=“SERVICE”>
                  <crv:memberClass>xxxxxx</crv:memberClass>
                  <crv:memberCode>xxxxxx</crv:memberCode>
                  <crv:subsystemCode>xxxxxxxx</crv:subsystemCode>
                  <crv:serviceCode>xxx</crv:serviceCode>
     </trp:service>
 </SOAP-ENV:Header>

This is what I have so far, but I am struggling to build the nested objectType in the header

     {
        "trp:protocolVersion" => 4.0
        "trp:id" => id,
        "trp:userId" => user_id

        "trp:service" => {
          '',
          :attributes!=> {
            'trp:service' => {'objectType' =>'SERVICE'}} },
      }