Support client.authentication.k8s.io/v1beta1

[jglick]

Amends #1224 to support the current apiVersion documented here. With #1347 worked around, this has been successfully tested on a GKE cluster using

users:
- name: gcp
  user:
    exec:
      apiVersion: "client.authentication.k8s.io/v1beta1"
      command: "sh"
      args:
        - "-c"
        - |
            gcloud config config-helper --format=json | jq '{"apiVersion": "client.authentication.k8s.io/v1beta1", "kind": "ExecCredential", "status": {"token": .credential.access_token, "expirationTimestamp": .credential.token_expiry}}'

(The gcloud container clusters get-credentials command recommended by Google rewrites your ~/.kube/config to use

users:
- name: …
  user:
   auth-provider:
     name: gcp
     config:
       access-token: …
       cmd-args: config config-helper --format=json
       cmd-path: gcloud
       expiry: …
       expiry-key: '{.credential.token_expiry}'
       token-key: '{.credential.access_token}'

which Config does not support, and which I think is semi-deprecated.)

[centos-ci]

Can one of the admins verify this patch?

[rohanKanojia]

ok to test

[rohanKanojia]

Thanks 👍

[rohanKanojia]

[merge]