presto-client/src/main/java/io/prestosql/client/StatementClientV1.java/StatementClientV1/prepareRequest
class StatementClientV1:    private Request.Builder prepareRequest(HttpUrl url)
    {
        return new Request.Builder()
                .addHeader(PRESTO_USER, user)
                .addHeader(USER_AGENT, USER_AGENT_VALUE)
                .url(url);
    }