PSA: Exposing "duplex" on Request

[Yoav Weiss (@Shopify)]

It seems like we shipped streamed requests without shipping the corresponding "duplex" attribute on Request objects.

As a result, we have a bug when trying to construct a Request with another Request that has a body, that's been biting developers in the wild.

I'm planning to add the "duplex" attribute on Request in order to fix that.

From my perspective, this is a bug fix with no compat or interop risk - other vendors haven't implemented the "duplex" attribute, but they don't support streaming requests either, so developers don't run into similar bugs there.

Please let me know if anyone believes this requires an intent. 

Cheers :)

Yoav