@Override
    public void handle(NotificationDto<AccountSignupEvent> signupNotification, Map<String, Object> defaultTemplateMap) {
        // Beware, for this instance, the user might not actually exist in Apiman (yet or at all) as it could have come
        // from the underlying IDM -- be careful if calling for Apiman's members, etc.
        UserDto recipient = signupNotification.getRecipient();

        mailNotificationService
             .findTemplateFor(signupNotification.getReason(), recipient.getLocale())
             .ifPresentOrElse(
                     template -> send(recipient, template, defaultTemplateMap),
                     () -> warnOnce(recipient, signupNotification)
             );
    }
@author Marc Savy {@literal <marc@blackparrotlabs.io>}
manager/api/rest-impl/src/main/java/io/apiman/manager/api/notifications/email/handlers/AccountSignupApprovalEmailNotification.java