// +union
message Subject {
  // `kind` indicates which one of the other fields is non-empty.
  // Required
  // +unionDiscriminator
  optional string kind = 1;

  // `user` matches based on username.
  // +optional
  optional UserSubject user = 2;

  // `group` matches based on user group name.
  // +optional
  optional GroupSubject group = 3;

  // `serviceAccount` matches ServiceAccounts.

// +union
message Subject {
  // `kind` indicates which one of the other fields is non-empty.
  // Required
  // +unionDiscriminator
  optional string kind = 1;

  // `user` matches based on username.
  // +optional
  optional UserSubject user = 2;

  // `group` matches based on user group name.
  // +optional
  optional GroupSubject group = 3;

  // `serviceAccount` matches ServiceAccounts.

  //  "timestamping", "ocsp signing", "microsoft sgc", "netscape sgc"
  // +listType=atomic
  repeated string usages = 5;

  // username contains the name of the user that created the CertificateSigningRequest.
  // Populated by the API server on creation and immutable.
  // +optional
  optional string username = 2;

  // uid contains the uid of the user that created the CertificateSigningRequest.

// +union
message Subject {
  // `kind` indicates which one of the other fields is non-empty.
  // Required
  // +unionDiscriminator
  optional string kind = 1;

  // `user` matches based on username.
  // +optional
  optional UserSubject user = 2;

  // `group` matches based on user group name.
  // +optional
  optional GroupSubject group = 3;

  // `serviceAccount` matches ServiceAccounts.

// +union
message Subject {
  // `kind` indicates which one of the other fields is non-empty.
  // Required
  // +unionDiscriminator
  optional string kind = 1;

  // `user` matches based on username.
  // +optional
  optional UserSubject user = 2;

  // `group` matches based on user group name.
  // +optional
  optional GroupSubject group = 3;

  // `serviceAccount` matches ServiceAccounts.