fetch-proxy redirect mode support

[jrestall]

I would really like if I could configure the redirect mode and other RequestInit properties as below.

const response = await proxy(request, { redirect: "manual" });

The fetch proxy seems to only respect a few of the init props passed in.

[mjackson]

You make a great point. We should absolutely respect all properties of the request init object in the proxy. I can take a look and get this fixed.

Other than redirect: "manual", were there any other specific properties you were interested in seeing support for?

[jrestall]

Thanks Michael, redirect is the only one I need, but maybe referrer and referrerPolicy for overriding the referrer in the proxy would be useful. Also signal maybe to support cancelling the proxy request if some other parallel request fails or to support a request timeout.

[jrestall]

Maybe also some learnings can be taken from hono's recent proxy implementation.

https://github.com/honojs/hono/blob/main/src/helper/proxy/index.ts

e.g.

1. Deletion of the hop by hop request/response headers. https://datatracker.ietf.org/doc/html/rfc2616#section-13.5.1
2. accept-encoding request header deletion, or handling of response encoding.
3. content-encoding and content-length response header deletion.
4. Passing of the full requestInit to the proxy request.