@Override
  public String toString() {
    StringBuilder buf = new StringBuilder();
    buf.append("AuthenticationKey[").append("id=").append(id).append(", expiration=")
      .append(Instant.ofEpochMilli(this.expirationDate)).append(", obj=").append(super.toString())
      .append("]");
    return buf.toString();
  }
Represents a secret key used for signing and verifying authentication tokens by
{@link AuthenticationTokenSecretManager}.
hbase-server/src/main/java/org/apache/hadoop/hbase/security/token/AuthenticationKey.java