Previously, site replication required the root credentials of peer sites to be identical. This is no longer necessary because STS tokens are now signed with the site replicator service account credentials, thus allowing flexibility in the independent management of root accounts across sites and the ability to disable root accounts eventually.

// +protobuf.options.(gogoproto.goproto_stringer)=false
message ExtraValue {
  // items, if empty, will result in an empty slice

  repeated string items = 1;
}

// TokenRequest requests a token for a given service account.
message TokenRequest {
  // Standard object's metadata.
  // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
  // +optional

* Designed with Helm best practices in mind (standardized values options, values schema, values are not all nested under `gateways.istio-ingressgateway.*`, release name and namespace taken into account, etc).
* Utilizes Gateway injection, simplifying upgrades, allowing gateways to run in any namespace, and avoiding repeating config for sidecars and gateways.
* Published to official Istio Helm repository.

  // if a fstype is defined and the volume's access mode contains ReadWriteOnce.
  //
  // +optional
  optional string fsGroupPolicy = 5;

  // tokenRequests indicates the CSI driver needs pods' service account
  // tokens it is mounting volume for to do necessary authentication. Kubelet
  // will pass the tokens in VolumeContext in the CSI NodePublishVolume calls.

  // This list may be empty, but only if `clusterScope` is true.
  // +optional
  // +listType=set
  repeated string namespaces = 5;
}

// ServiceAccountSubject holds detailed information for service-account-kind subject.
message ServiceAccountSubject {
  // `namespace` is the namespace of matching ServiceAccount objects.
  // Required.
  optional string namespace = 1;

  // This list may be empty, but only if `clusterScope` is true.
  // +optional
  // +listType=set
  repeated string namespaces = 5;
}

// ServiceAccountSubject holds detailed information for service-account-kind subject.
message ServiceAccountSubject {
  // `namespace` is the namespace of matching ServiceAccount objects.
  // Required.
  optional string namespace = 1;

    - creates service-account `istio-cni` with `ClusterRoleBinding` to allow gets on pods' info and delete/modifications for recovery.

- `install-cni` container
    - copies `istio-cni` and `istio-iptables` to `/opt/cni/bin`
    - creates kubeconfig for the service account the pod runs under
    - periodically copy the K8S JWT token for istio-cni on the host to connect to K8S.

  // Pods are only limited to this list if this service account has a "kubernetes.io/enforce-mountable-secrets" annotation set to "true".
  // This field should not be used to find auto-generated service account token secrets for use outside of pods.
  // Instead, tokens can be requested directly using the TokenRequest API, or service account token secrets can be manually created.

  // 'request' - Attributes of the admission request(/pkg/apis/admission/types.go#AdmissionRequest).
  // 'authorizer' - A CEL Authorizer. May be used to perform authorization checks for the principal (user or service account) of the request.
  //   See https://pkg.go.dev/k8s.io/apiserver/pkg/cel/library#Authz
  // 'authorizer.requestResource' - A CEL ResourceCheck constructed from the 'authorizer' and configured with the
  //   request resource.

* The `kube-cloud-controller-manager` flag `--service-account-private-key-file` was non-functional and is now deprecated. ([#50289](https://github.com/kubernetes/kubernetes/pull/50289), [@liggitt](https://github.com/liggitt))
    * The `kube-cloud-controller-manager` flag `--use-service-account-credentials` is now honored consistently, regardless of whether `--service-account-private-key-file` was specified.