CLIENT_CERT http-authentication-mechanism currently requires to provide security-realm, which will contain identity for given certificate and will verify X509Evidence for it. This does not provide replacement for legacy truststore auth, which allows to use only CA certificate to authenticate users by certificates signed by CA, without any database of them.

Analysis document:
https://developer.jboss.org/wiki/AnalysisDesign-CLIENTCERTWithoutUsersCertificatesDatabase