Camunda-webapp 7.21.0 SSO login

Hello,

I need a help with SSO authorization to camunda webapp.
Until now, we used to run camunda wepapp on version 7.12.0. We used our own auth server for authorization and by usage of org.camunda.bpm.webapp.impl.security.auth.ContainerBasedAuthenticationFilter
and our own implementation of
org.camunda.bpm.engine.rest.security.auth.impl.ContainerBasedAuthenticationProvider
we used our own users to login to camunda wepapp. These users were never saved in camunda database.

We are now trying to migrate to camunda 7.21.0. However in 7.19.0
org.camunda.bpm.webapp.impl.security.auth.AuthenticationUtil
was introduced, which replaced
org.camunda.bpm.webapp.impl.security.auth.AuthenticationService
And in this
AuthenticationUtil.createAuthentication(ProcessEngine processEngine, String username, List groupIds, List tenantIds)
after fetching user from camunda database a new condition was added
if (user == null) {
return null;
}
due to which I cannot use our own users, which are not saved in camunda database.
Is it ment to be like that?
How can I get over that user null check?

Thank you