Add ingressClassName field to Ingress trait

[lsergio]

Requirement

The Ingress spec has the ingressClassName field which is a replacement for the deprecated kubernetes.io/ingress.class annotation.
I think it might be interesting to add the ingressClassName field to the Ingress trait to be compatible with the recommended way of defining the class name.

Problem

It doesn't really block me from creating the Ingress. It will be a problem if the deprecated annotation someday becomes unsupported.

Proposal

Just add the field to the Ingress trait as a non-required information and copy it to the corresponding Ingress attribute.

Open questions

No response

[lsergio]

I can work on that if it's a good idea.

[squakez]

Yeah thanks, it would be great.