Httpx includes ipv6 scope in Host header

Originally opened by @elupus on 2022-04-11 14:43:59 in encode/httpx

When requesting http paths with scope as part of the ipv6 address, this should stripped before being added to the http host header since it's fully local feature of the ipv6 stack.

Http over link local addresses is quite common on upnp based announces on link local networks.

Apache for example will reject the request: https://bz.apache.org/bugzilla/show_bug.cgi?id=35122
Lighthttpd: https://redmine.lighttpd.net/issues/2442

Example to reproduce:

import httpx
import respx

`@respx`.mock
def test_example():
    my_route = respx.get("https://[fe80::8fd:8e9a:40d8:29a6%en0]/get")
    my_route.mock(return_value=httpx.Response(204))

    r = httpx.get(r'https://[fe80::8fd:8e9a:40d8:29a6%en0]/get')

    print(my_route.calls[0].request.headers["host"])
    assert my_route.calls[0].request.headers["host"] == "[fe80::8fd:8e9a:40d8:29a6]"

test_example()

• Initially raised as discussion #...

Start with the test_example reproduction using httpx and respx, then trace how the request URL becomes the HTTP Host header. The work is done when the shown assertion passes for a scoped IPv6 address without regressing ordinary host headers.