Forwarding files to another service.
Hello,

First of all, thank you for this awesome library :)

I have a question: How do you suggest forwarding the files that we receive in a resolver to another service? Currently, I write the file locally with `stream.pipe(createWriteStream(filename))` and then forward that file to the other service that I want. But I think there should be a better way to achieve this.

Is it BusBoy that is stopping me from doing that? Because, I remember looking at _formidable_ and it gives me the entire file object, but BusBoy seems to only give few of the fields from the File object and does some 'magic' under the hood?