private static Map<String, CandidateRecipientAddress> getSmsRecipients(final RequestContext requestContext) {
        return (Map<String, CandidateRecipientAddress>) requestContext.getFlowScope().get(FLOW_SCOPE_ATTR_SMS_RECIPIENTS, Map.class);
    }
Event attribute to allow registration of email.
support/cas-server-support-simple-mfa-core/src/main/java/org/apereo/cas/mfa/simple/web/flow/CasSimpleMultifactorSendTokenAction.java