My idea is that `field_encoding_style` would be set by calling application code. Use case: some appl specifically designed to talk to some server which does not follow HTML 5 but which does support RFC2231. Then the app would set the style for each request it generates, or for its own derived request class. That's what I'd like to document, and still haven't decided on where to put that.

`form_data_encoding` would be handled in a similar way, except that in that case I can also imagine a more dynamic approach: Consider a web robot application could set that parameter on a request which it creates in response to some HTML file that got transferred using latin1.