fetch() keeps the original URL after redirects

[Monti-27]

fetch() follows redirects, but the resulting Response still reports the original URL and redirected === false.

Repro against a local server that returns 302 Location: /target#frag:

const r = await fetch("http://127.0.0.1:8131/redirect");
console.log(r.redirected, r.url);

Current Boa:

• false
• http://127.0.0.1:8131/redirect

Expected:

• true
• http://127.0.0.1:8131/target

This matches Node and the Fetch spec for Response.redirected and Response.url.

[Cypher-CP0]

Hi! I'd like to take a stab at fixing this.
From reading the WHATWG Fetch spec, the issue is that Response.url should reflect the final URL after following redirects (last entry in the internal URL list, minus fragment), and Response.redirected should be true if the URL list has more than one entry.
My plan: in boa_runtime's fetch implementation, after reqwest resolves the final response, use reqwest_response.url() for the Response.url field (instead of the original request URL), and derive Response.redirected by comparing the original and final URLs (or checking redirect history). I'll also add a test with a local redirect server to cover this case.
Will raise a PR shortly!