feat(cmd/anubis): compute full XFF header (#328)

* feat(cmd/anubis): compute full XFF header

this one is pretty important to not pass
through blindly, as many applications and
frameworks will trust them

* feat(cmd/anubis): skip XFF compute if remote address is loopback

* docs: update CHANGELOG

cmd/anubis/main.go

@@ -280,6 +280,7 @@ func main() {
 	h = s
 	h = internal.RemoteXRealIP(*useRemoteAddress, *bindNetwork, h)
 	h = internal.XForwardedForToXRealIP(h)
+	h = internal.XForwardedForUpdate(h)
 
 	srv := http.Server{Handler: h}
 	listener, listenerUrl := setupListener(*bindNetwork, *bind)