Different user database depending on client_id

[guillerodriguez]

I have an application where the user database should be different depending on the client_id parameter.

This does not seem to be supported out of the box: the checkUserCredentials and getUserDetails methods in UserCredentialsInterface don't receive the client_id parameter.

I considered the possibility to subclass UserCredentials::validateRequest instead but this method needs to update the private $userInfo variable, which cannot be done from a subclass.

What is the recommended way to do this?
Is there a way to specify a different storage for the user database depending on client_id?
Other alternatives?