Add `gke-security-groups` Google Group for Kubernetes RBAC

[Brett Curtis]

Cluster Administrators should leverage G Suite Groups and Cloud IAM to assign Kubernetes user roles to a collection of users instead of individual emails using only Cloud IAM.

This is related to: osinfra-io/terraform-google-kubernetes-engine#14

We ultimately need the onboarding code to create and manage nested groups under

Tasks

Beta Give feedback

1. Group created
2. Can manage nested groups
3. Modify issue template to include a checkbox for nested GKE security groups

Documentation:

• https://cloud.google.com/kubernetes-engine/docs/how-to/google-groups-rbac