Contour: Support ingress.kubernetes.io/auth-{type,secret,realm}

[davecheney]

Add support for

• ingress.kubernetes.io/auth-type
• ingress.kubernetes.io/auth-secret
• ingress.kubernetes.io/auth-realm

Annotations.

[domhauton]

Without this there is no (easy) way to protect ingress endpoints with oauth2.

https://eng.fromatob.com/post/2017/02/lets-encrypt-oauth-2-and-kubernetes-ingress/

[swade1987]

Would be great to have the equivalent of

nginx.ingress.kubernetes.io/auth-signin: "https://auth.oidc.example.co.uk/oauth2/start?rd=https://$host$request_uri$is_args$args"
nginx.ingress.kubernetes.io/auth-url: "https://auth.oidc.example.co.uk/oauth2/auth"