GetVersionedClientForRBACOrFail discovers the versioned rbac APIs and gets the versioned clientset for either the preferred version or the first listed version (if no preference listed) TODO: We need to evaluate the usage of RESTMapper interface to achieve te same functionality.

NewAdminConfig creates an admin config for `kubefed` commands.

DefaultFederationSystemNamespace is the namespace in which federation system components are hosted.

Used in and to create the kube-dns configmap storing the zone info.

KubeconfigSecretDataKey is the key name used in the secret to stores a cluster's credentials.

used to identify the rbac api availability error.

SubcommandOptions holds the configuration required by the subcommands of `kubefed`.

AdminConfig provides a filesystem based kubeconfig (via `PathOptions()`) and a mechanism to talk to the federation host cluster and the federation control plane api server.