@Override
    public String getAuditablePrincipal() {
        return StringUtils.defaultIfBlank(claims.getClaimValueAsString("sub"), PrincipalResolver.UNKNOWN_USER);
    }
This is {@link OidcIdToken}.

@author Misagh Moayyed
@since 7.0.0
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/ticket/idtoken/OidcIdToken.java