void send(UserDto recipient, EmailNotificationTemplate template, Map<String, Object> defaultTemplateMap) {
        var mail = SimpleEmail
                .builder()
                .setRecipient(recipient)
                .setTemplate(template)
                .setTemplateVariables(defaultTemplateMap)
                .build();

        mailNotificationService.send(mail);
    }
@author Marc Savy {@literal <marc@blackparrotlabs.io>}
manager/api/rest-impl/src/main/java/io/apiman/manager/api/notifications/email/handlers/ClientAppRegisteredEmailNotification.java