Describe the solution

We are using the Miniflare with the upstream option as a proxy. Yet, we need to know which is the host origin.

When using the upstream option, the headers Host and Forwarded-Host becomes the upstream, losing the original hostname along the way.

We need this because we have multiple domains, so, rewriting the Forwarded-Host with a constant isn't an option.

But, if Miniflare stores the information in a header, like X-MINIFLARE-ORIGINAL-HOSTNAME, we can reuse that on outboundService function, and other functions using the workerContext.