Incorrect value for X-Forwarded-Proto

[Tristan971]

Environment

Irrelevant but Nitro 2.8.1 on Node 20.5

Reproduction

Issue is visible in:

https://github.com/unjs/nitro/blob/06323b736f0d8adaa609d5a0348fa6b9e0db75e7/src/dev/server.ts#L203-L205

Describe the bug

The X-Forwarded-Proto header should take a value in [http, https], and instead takes a value in [IPv4, IPv6]

With the current code, accessing a Nitro server with plaintext results in X-Forwarded-Proto: IPv4 (for example)

This is not correct, and should instead give X-Forwarded-Proto: http

Additional context

Since it is not a standardised header, the best source of documentation is your pick between:
a. The Mozilla docs about the de-facto way it is meant to work: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto#syntax
b. The spec for the Forwarded header which is based on it (and other X-Forwarded-* friends): https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded#proto
c. Nearly every (widespread) webserver in existence (CF: https://developers.cloudflare.com/fundamentals/reference/http-request-headers/#x-forwarded-proto, AWS: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/x-forwarded-headers.html#x-forwarded-proto, HAProxy: https://docs.haproxy.org/2.8/configuration.html#7.3.1-iif, ...)

Logs

No response

[dpmillerau]

This is causing me a problem implementing tus-node-server in nuxt

[manniL]

Seems reasonable IMO. PR Welcome 👍🏻