Use internal kubernetes service for forwardAuth

Hi,

I am trying to use the foward-auth middleware and I need to point the forwarding address to an internal k8s service. I tried the fully-qualified DNS address http://[name].[namespace].svc.cluster.local:[port], but it does not get resolved.

Logs:

{"level":"debug","middlewareName":"xxx@kubernetescrd","middlewareType":"ForwardedAuthType","msg":"Error calling http://mysvc.myns.svc.cluster.local:<port>. Cause: Get \"http://mysvc.myns.svc.cluster.local:<port>\": dial tcp: lookup mysvc.myns.svc.cluster.local on <some-ip>:53: no such host","time":"2022-12-28T14:48:02Z"}

The DNS name seems invalid, this is rather a Kubernetes than a Traefik issue.

You can go into your Traefik container and try wget http://url to see which URL works.