Need documentation around using GKE ingress with Portainer

[joshua-portainer]

It would be helpful to have documentation outlining the steps required to setup GKE ingress with Portainer.

[jtraxy]

Although https://docs.portainer.io/user/kubernetes/cluster/setup talks about IngressClass-less ingress controllers in general terms, perhaps we could have a section specifically about the GKE Ingress controller. I suggest something like this:

GKE Ingress Controller
Google Cloud ingress controller (gce or GKE Ingress) continues to use the deprecated kubernetes.io/ingress.class annotation on ingresses, whereas most other ingress controllers use the IngressClass resource that was introduced in Kubernetes 1.18. Portainer targets the IngressClass resource means of specifying ingress classes, but you can still use Google Cloud ingress controllers by turning on the 'Allow ingress class to be set to "none"' toggle in Cluster setup and setting them up as custom with "none" selected as their class. Then when adding an ingress based on this, set the an annotation of key 'kubernetes.io/ingress.class' and value 'gce'.

[jtraxy]

Actually, this has been added as an info note in https://docs.portainer.io/user/kubernetes/ingresses/add - so all good.
James C. mentioned that he will link kubernetes/cluster/setup documentation page to that info note too.