@Override
        public void sendHtml(String toEmail, String toName, String subject, String htmlBody, String plainBody, Map<String, String> headers) throws EmailException {

        }
Map: Reason code -> email notification template.
Helpful for making Jackson deserialization a bit easier.
manager/api/rest-impl/src/main/java/io/apiman/manager/api/notifications/email/SimpleMailNotificationService.java