container download support does not work with @href (uri)

Even though apache/grails-geb#74 works, I currently have to use this workaround for downloading from a controller-offered download link (@ href) (https://www.gebish.org/manual/current/#downloading-example):

```
// https://github.com/grails/geb/issues/132
static String remove_host_from_uri(href) {
URI uri = new URI(href as String)
String relativePath = uri.getRawPath() + (uri.getRawQuery() ? '?' + uri.getRawQuery() : '')
return relativePath
}
```

Problem: see https://github.com/apache/grails-core/issues/14330

Start by reproducing the controller-offered download link described in the Geb downloading example and compare it with the URI workaround shown in the issue. Trace how the container handles the @href value; done means downloads work directly from that URI without removing the host manually.

Written by the indexing model from the issue text.