Can you help me to build the following XML using Builder gem

```
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
    <soapenv:Header/>
    <soapenv:Body>
        <Service>
            <Source ID="1" Name="A"></Source>
        </Service>
    </soapenv:Body>
</soapenv:Envelope>

```

So far I ended up with this

```
builder = Builder::XmlMarkup.new
builder.instruct!(:xml, :encoding => "UTF-8")
builder.service { |p| p.source }

```

Thanks!