Add the ability to limit the max amount of openings a user can claim.

Problem/Motivation

Currently, we are limiting the most amount of spots a user can claim with a single booking, but they could just book it again and claim more spots. They also could book the same time slot every single day forever, which might not be desired.

Proposed resolution

Much like how there is a field for "Max Party Size" we could add a new field to limit max open bookings per user, and you should be able to in theory set different values on that base on user role. If you are not requiring users to be logged in when booking, we can do a quantity check vs the emails supplied.

I would assume we would be limiting this based on openings in the future, not total all time for this calendar, but I guess people might want it that way too, so I'm trying to think if there's a way to handle both situations.

Also with this we probably need to start breaking up the UI for the entity form as it's starting to get a little long, might be nice to reorganize this and maybe split up into different collapsible sections.