Support /stats, /metrics and /ui endpoints on different port

In production deployments It may desired to expose swagger-stats on different port, so it can only be accessed internally. Support configuration to serve /stats, /metrics and /ui endpoints on different ( management ) port.

+1 Do you know if it's possible to do it with this library? I got really useful help in another library which might be useful for you also. https://github.com/jochen-schweizer/express-prom-bundle/issues/25