HTTP Path Prepending
fabio supports prepending a path to the incoming request. If you want to
forward http://host/bar as http://host/foo/bar you can add a prepend=/foo
option to the route options as urlprefix-/bar prepend=/foo.
Path prepending is done after path stripping. If you want to
forward http://host/foo/bar as http://host/baz/bar you can add
prepend=/baz and strip=/foo options to the route options as
urlprefix-/bar prepend=/baz strip=/foo.