default String getPrincipalFromRecordKey(final String key) {
        return Iterables.get(Splitter.on('@').split(key), 0);
    }
Gets principal from record key.

@param key the key
@return the principal from record key
support/cas-server-support-trusted-mfa-core/src/main/java/org/apereo/cas/trusted/authentication/api/MultifactorAuthenticationTrustRecordKeyGenerator.java