`fetch` can send conflicting :authority and host headers on HTTP/2

[magurotuna]

Problem

using client = Deno.createHttpClient({ allowHost: true });
const res = await fetch("https://example.com", {
  client,
  headers: {
    host: "example.net",
  },
});
console.log(res.status);

We expect this code to send :authority = example.net (instead of example.com). But what's actually sent is :authority = example.com and host = example.net, which violates the HTTP/2 RFC (see RFC 9113 §8.3.1).

Here is the wireshark screenshot, showing the request made by the script above contained conflicting :authority and host

Additional info

Version: Deno 2.6.9

[magurotuna]

I sent a patch to the upstream h2 crate to address this issue. hyperium/h2#877
I confirmed that the issue is resolved with this patch applied to Deno.