@Override
    public Optional<ByteArray> getUserHandleForUsername(final String username) {
        return getRegistrationsByUsername(username)
            .stream()
            .findAny()
            .map(reg -> reg.getUserIdentity().getId());
    }
This is {@link BaseWebAuthnCredentialRepository}.

@author Misagh Moayyed
@since 6.3.0
support/cas-server-support-webauthn-core/src/main/java/org/apereo/cas/webauthn/storage/BaseWebAuthnCredentialRepository.java