Permission plugin improvements

[aleksip]

This adds context parameter support to the permission controller plugin.

An optional separate commit also adds a getIdentity() method which I have found useful to have here, but am not completely sure if the permission plugin should provide such functionality.

[demiankatz]

Thanks, @aleksip, this makes sense to me.

It may actually be a helpful project to see if there are any places in the code where we can rely on \LmcRbacMvc\Identity\IdentityInterface instead of \VuFind\Db\Row\User. One big remaining piece of the Doctrine migration in #2233 is to refactor the login and identity management code away from Laminas\Db, and if we can reduce the general reliance of the code on the Laminas user row object, that work will likely be simplified. Not sure how likely that is to make a big difference, but it might be worthwhile to investigate at least.