code: func (t *TestTLSServer) CertPool() (*x509.CertPool, error) {
  	tlsConfig, err := t.Identity.TLSConfig(t.AuthServer.CipherSuites)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return tlsConfig.RootCAs, nil
  }
docs: // CertPool returns cert pool that auth server represents