With Go 1.20 the "Rewrite" hook for ReverseProxy was introduced to
supersede of the "Director" hook (see:
https://github.com/golang/go/commit/a55793835f16d0242be18aff4ec0bd13494175bd)
The Rewrite hooks allows for better separation between the incoming and
outgoing request. In particular it makes it pretty easy to set the
correct X-Forwarded-* Headers on the outgoing request.
The need for using "Rewrite" came up when trying to embed
authelia. It uses the X-Forwarded-Host and X-Forwared-Proto headers to
e.g. compute the correct return values for the various endpoints in
.well-known/openid-configuration.
I refactored the proxy so that we execute the routing before the
authentication middleware. This is necessary so that we can determine
which routes are considered unprotected i.e. which routes don't need
authentication.
