outbound-http: Remove host header with http2 (#3194)

The HTTP/2 spec allows the host header to be set as long as it matches
:authority, but some servers seem to have trouble accepting this
reality: hyperium/hyper#3298

Signed-off-by: Lann Martin <lann.martin@fermyon.com>

Author: lann

crates/factor-outbound-http/src/wasi.rs

@@ -330,7 +330,11 @@ async fn send_request_handler(
         (sender, worker, is_http2)
     };
 
-    if !is_http2 {
+    if is_http2 {
+        // Some servers (looking at you nginx) don't like a host header even though
+        // http/2 allows it: https://github.com/hyperium/hyper/issues/3298
+        request.headers_mut().remove(HOST);
+    } else {
         // at this point, the request contains the scheme and the authority, but
         // the http packet should only include those if addressing a proxy, so
         // remove them here, since SendRequest::send_request does not do it for us