Imports k8s.io/apimachinery/pkg/util/errors k8s.io/apimachinery/pkg/util/sets k8s.io/apiserver/pkg/authentication/authenticator k8s.io/apiserver/pkg/authentication/user k8s.io/client-go/util/cert Standard library imports crypto/x509 crypto/x509/pkix encoding/hex fmt net/http strings