Extend patron expire date with activity

Wishlist:

Automatically extend a patron's expire date if the patron is using the system. "Using the system" can be defined as having entries in actor.usr_activity, which captures the simplest patron activity (e.g. logging in to the catalog, via SIP, etc.), which is important for patrons that may never actually enter a library, but are clearly using it.

Providing a way to avoid updating certain groups (e.g. a bool on permission.grp_tree) would also be needed. Perhaps this would be set to false for all groups by default.

The update interval would be the perm_interval on permission.grp_tree or potentially a static configured value.

I could see this happening in a nightly process or in real time, assuming the real-time version doesn't cause any delays. I'd lean toward nightly batches, because it's not an urgent process. IOW, if the patron can log in, and thus have not expired, updating the expire date *right now* serves little purpose.