Set `appProtocol` on Services

[johanfleury]

Is your feature request related to a problem? Please describe.

On GKE, with an HTTPRoute the Load Balancer uses the Service's spec.port[].appProtocol to determine what protocol to use yo reach the backend (HTTP or HTTPS). If absent, it defaults to HTTP.

You can encrypt traffic from the load balancer to backend Pods using the ports[].appProtocol field. The supported fields for appProtocol are: HTTP, HTTPS, HTTP2, and kubernetes.io/h2c.

Describe the solution you'd like

Automatically set appProtocol to HTTP or HTTPS based om whether TLS is enabled or not.

Describe alternatives you've considered

As far as I know, no alternatives exist. GKE doesn't support TLS passthrough via TLSRoutes (yet?).

[eyenx]

Thanks for reaching out and creating this issue including the PR