message ClusterTrustBundleSpec {
  // signerName indicates the associated signer, if any.
  //
  // In order to create or update a ClusterTrustBundle that sets signerName,
  // you must have the following cluster-scoped permission:
  // group=certificates.k8s.io resource=signers resourceName=<the signer name>
  // verb=attest.
  //
  // If signerName is not empty, then the ClusterTrustBundle object must be

  //  3. Otherwise, it is assigned "kubernetes.io/legacy-unknown".
  // Distribution of trust for signers happens out of band.
  // You can select on this field using `spec.signerName`.
  // +optional
  optional string signerName = 7;

  // expirationSeconds is the requested duration of validity of the issued
  // certificate. The certificate signer may issue a certificate with a different