Currently if your circ manager runs two different Enki libraries, you need to set up two different collections with protocol="Enki" and two different library IDs.

It turns out this is very wasteful – the Enki collection has over 40,000 items in it, and it's the exact same 40,000 items for every library. There is no reason to have two different collections – we only need to be able to provide the appropriate library ID when we're borrowing a book.

That is to say, Enki "library ID" turns out to be less like Overdrive "library ID" and more like Overdrive "ILS name". If we moved "library ID" out of EnkiAPI.SETTINGS and into EnkiAPI.LIBRARY_SETTINGS, it would be possible to associate multiple libraries with a single Enki collection. The documentation for the Enki API expects every request to contain a library ID as "lib", but for most API requests it works fine if "lib" is left blank. It looks like we can provide "lib" when we're acting on behalf of a specific library, and leave it blank at all other times.

It's not clear to me how to migrate a system that's already been set up with multiple Enki collections; that's likely to be the most difficult part of this change.