public void sendHtml(String toEmail, String toName, String subject, String htmlBody, String plainBody) {
        emailSender.sendHtml(toEmail, toName, subject, htmlBody, plainBody, DEFAULT_HEADERS);
    }
Send an HTML email with a plaintext fallback/alternative.
manager/api/rest-impl/src/main/java/io/apiman/manager/api/notifications/email/SimpleMailNotificationService.java