title: NetflixOSS Zuul Filter for rejecting requests
body: <p>I am trying to use a ZuulFilter in a simple spring-cloud-Netflix Api gateway (reverse proxy) in order to authenticate requests against a custom authentication provider (via Rest call). </p>
  
  <p>The Filter should reject unauthorized requests with a 401 and don't pass those requests further down to the proxied services.</p>
  
  <p>Is that even possible for a ZuulFilter? I did not find documentation, example or something in Zuuls api. </p>
  
  <p>Any suggestions? </p>