@Deprecated
  public String getServerPrincipal() {
    return serverPrincipals.get(0);
  }
Although this class is IA.Private, we leak this class in
{@code SaslClientAuthenticationProvider}, so need to align with the deprecation cycle for that
class.
@deprecated Since 2.6.0, will be removed in 4.0.0. Use {@link #getServerPrincipals()} instead.
hbase-client/src/main/java/org/apache/hadoop/hbase/security/SecurityInfo.java