Update tame-oauth to 0.6.0

[kazk]

Application Default Credentials from gcloud, and obtaining OAuth tokens from local metadata server when running inside GCP are now supported.

See #644

[clux]

That looks great to me. Are you testing with GCP directly?

[kazk]

Are you testing with GCP directly?

I confirmed Application Default Credentials works (reading ~/.config/gcloud/application_default_credentials.json and making request).

I have some clusters on GCP (GKE), and it uses command-based authentication (gcloud config config-helper --format=json):

https://github.com/kube-rs/kube-rs/blob/afc85402c1900a2b5aa4f1f993abfc489f82dd37/kube-client/src/client/auth/mod.rs#L264-L265

So, I commented out cmd-path field in the provider config to make it use oauth instead.

I don't have anything to test the local metadata server auth with, though.

---

With the update, it should match what client-go is doing: https://github.com/kubernetes/kubernetes/blob/bbc3a9aace18ae40598e5279202cc67a89d7b9f3/staging/src/k8s.io/client-go/plugin/pkg/client/auth/gcp/gcp.go#L142-L170

But I just noticed gcp provider is deprecated since v1.22, and will be removed in v1.25:

https://github.com/kubernetes/kubernetes/blob/bbc3a9aace18ae40598e5279202cc67a89d7b9f3/staging/src/k8s.io/client-go/plugin/pkg/client/auth/gcp/gcp.go#L118-L124

func newGCPAuthProvider(_ string, gcpConfig map[string]string, persister restclient.AuthProviderConfigPersister) (restclient.AuthProvider, error) {
	// deprecated in v1.22, remove in v1.25
	// this should be updated to use klog.Warningf in v1.24 to more actively warn consumers
	warnOnce.Do(func() {
		klog.V(1).Infof(`WARNING: the gcp auth plugin is deprecated in v1.22+, unavailable in v1.25+; use gcloud instead.
To learn more, consult https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins`)
	})

I guess it's going to be replaced by exec: {command: gcloud}.