What’s the best way to implement Access Control Protocol on my WebDAV server that uses generic streams for resources, so that it can be agnostic to storage systems through adapters like the file system adapter?

I was thinking to have another kind of adapter for users/groups/permissions. Or should I add that functionality to the existing adapters? I’m not sure how to proceed.

It also needs to work with generic authenticators, like this one that authenticates with PAM.