presto-client/src/main/java/io/prestosql/client/SpnegoHandler.java/SpnegoHandler/authenticate
class SpnegoHandler:    private Request authenticate(Request request)
    {
        String hostName = request.url().host();
        String principal = makeServicePrincipal(servicePrincipalPattern, remoteServiceName, hostName, useCanonicalHostname);
        byte[] token = generateToken(principal);

        String credential = format("%s %s", NEGOTIATE, Base64.getEncoder().encodeToString(token));
        return request.newBuilder()
                .header(AUTHORIZATION, credential)
                .build();
    }