code: func (a *TestAuthServer) NewCertificate(identity TestIdentity) (*tls.Certificate, error) {
  	cert, key, err := GenerateCertificate(a.AuthServer, identity)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	tlsCert, err := tls.X509KeyPair(cert, key)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return &tlsCert, nil
  }
docs: // NewCertificate returns new TLS credentials generated by test auth server