[focalboard] Ingress missing ingressClassName

[maxirus]

With networking.k8s.io/v1, the Class.Spec expects the attribute ingressClassName.

Example:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
#...
spec:
  ingressClassName: nginx

ingressClassName should be configurable via .Values

[bbaptist]

This is a duplicate of #288