Automatic merge from submit-queue (batch tested with PRs 41349, 41532, 41256, 41587, 41657)
client-go: don't import client auth provider packages
Both of these auth providers are useful for kubectl but not so much for everyone importing client-go. Let users optionally import them (example [0]) and reduce the overall number of imports that client-go requires.
Quick grep seems to imply it wont import it after.
```
$ grep -r 'client-go/plugin/pkg/client/auth' staging/
staging/src/k8s.io/client-go/plugin/pkg/client/auth/plugins.go: _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
staging/src/k8s.io/client-go/plugin/pkg/client/auth/plugins.go: _ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
staging/src/k8s.io/client-go/examples/third-party-resources/main.go: _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
staging/src/k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/clientset.go: _ "k8s.io/client-go/plugin/pkg/client/auth"
staging/src/k8s.io/kube-aggregator/pkg/client/clientset_generated/internalclientset/clientset.go: _ "k8s.io/client-go/plugin/pkg/client/auth"
```
closes https://github.com/kubernetes/client-go/issues/49
updates https://github.com/kubernetes/client-go/issues/79 (removes cloud.google.com/go import)
cc @kubernetes/sig-api-machinery-pr-reviews @kubernetes/sig-auth-pr-reviews
```release-notes
client-go no longer imports GCP OAuth2 and OpenID Connect packages by default.
```
[0] 8b466d64c5/examples/third-party-resources/main.go (L34-L35)
Automatic merge from submit-queue (batch tested with PRs 41112, 41201, 41058, 40650, 40926)
Promote TokenReview to v1
Peer to https://github.com/kubernetes/kubernetes/pull/40709
We have multiple features that depend on this API:
- [webhook authentication](https://kubernetes.io/docs/admin/authentication/#webhook-token-authentication)
- [kubelet delegated authentication](https://kubernetes.io/docs/admin/kubelet-authentication-authorization/#kubelet-authentication)
- add-on API server delegated authentication
The API has been in use since 1.3 in beta status (v1beta1) with negligible changes:
- Added a status field for reporting errors evaluating the token
This PR promotes the existing v1beta1 API to v1 with no changes
Because the API does not persist data (it is a query/response-style API), there are no data migration concerns.
This positions us to promote the features that depend on this API to stable in 1.7
cc @kubernetes/sig-auth-api-reviews @kubernetes/sig-auth-misc
```release-note
The authentication.k8s.io API group was promoted to v1
```
Automatic merge from submit-queue (batch tested with PRs 39475, 38666, 39327, 38396, 39613)
Add checking the nil value
**What this PR does / why we need it**:
Add checking the nil value.
Thanks.
**Special notes for your reviewer**:
