Prior to this change, the request URI was only ever read from the
X-Forwarded-Uri header which was only set when the container was
accessed via the forwardauth middleware. As such, it was necessary
to apply the treafik-forward-auth middleware to the treafik-forward-auth
container when running auth host mode.
This is a quirk, unnecessary complexity and is a frequent source of
configuration issues.
c4317b7503