Avoid magic in DjangoGetter for FieldFile

[jakajancar]

I would like to create a custom schema for FieldFile that returns something like

{
    name: "...",
    url: "...",            // content-disposition: inline
    download_url: "...",   // content-disposition: attachment
    content_type: "...",   // guessed based on extension
}

Would expect it to not be a problem, just define a schema for the FileField property, however DjangoGetter automatically converts the result to result.url meaning you lose the original FieldFile and are now stuck with only the url.