Marshalling JWK with X.509 certs (x5c) to JSON is incorrect about jwx HOT 4 CLOSED

	if v, ok := h.Get(X509CertChainKey); ok {
		var chain []*x509.Certificate
		if chain, ok = v.([]*x509.Certificate); !ok {
			return fmt.Errorf("%s is of invalid type %T", X509CertChainKey, v)
		}
		encodedChain, err := marshalX509CertChain(chain)
		if err != nil {
			return err
		}
		m[X509CertChainKey] = encodedChain
	}

func marshalX509CertChain(chain []*x509.Certificate) ([]string, error) {
	encodedCerts := make([]string, len(chain))
	for idx, cert := range chain {
		encodedCerts[idx] = base64.StdEncoding.EncodeToString(cert.Raw)
	}
	return encodedCerts, nil
}