Include host in header to retrieve correct base url

First I used following request to retrieve a node based on url, while using the decoupled router module:

[{
    "requestId": "resolvedRoute",
    "action": "view",
    "uri": "/router/translate-path?path=/homepage&_format=json",
    "headers": {
        "Content-Type": "application/vnd.api+json"
    }
}]

But this only got me the following response:

"body": "{"resolved":"http://localhost/homepage","entity":{"canonical":"http://localhost/homepage","type":"node","bundle":"homepage","id":"9","uuid":"4e1f5a9b-5ed6-484f-ac21-583612fa21df"},"jsonapi":{"individual":"http://localhost/jsonapi/node/homepage/4e1f5a9b-5ed6-484f-ac21-583612fa21df","resourceName":"node--homepage","pathPrefix":"jsonapi"}}"

As you can see it always uses localhost instead of the correct base_url. When using the exact same request without subrequests this doesn't occur. So after some digging I figured out that this could be resolved by applying the Host parameter in my request header:

[{
    "requestId": "resolvedRoute",
    "action": "view",
    "uri": "/router/translate-path?path=/homepage&_format=json",
    "headers": {
        "Content-Type": "application/vnd.api+json",
        "Host": "host_url"
    }
}]

And now based on the Host parameter the correct base url is used throughout the response:

"body": "{"resolved":"host_url/homepage","entity":{"canonical":"host_url/homepage","type":"node","bundle":"homepage","id":"9","uuid":"4e1f5a9b-5ed6-484f-ac21-583612fa21df"},"jsonapi":{"individual":"host_url/jsonapi/node/homepage/4e1f5a9b-5ed6-484f-ac21-583612fa21df","resourceName":"node--homepage","pathPrefix":"jsonapi"}}"

@e0ipso

Above patch doesn't seem to resolve the issue.

It seems the if statement never gets executed due to the host (localhost) is always included in the $to headers.

    if (!$to->headers->get($name)) {
      $master_header = $from->headers->get($name);
      $to->headers->set($name, $master_header);
    }

If I always forward the master host to the subrequest it seems to work fine but this may cause some unexpected behavior maybe?