Support for holds pickup at 'pop-up libraries'

Some of our libraries are implementing pop-up libraries where they may go to an offsite location (the local senior center and maybe a mall) with a small collection of items that can be circulated to users.

We would like the system to support holds to be picked up at these pop-up libraries. Because we will have different hold policies for items picked up at pop-up libraries, we think the best approach is to set up an OU for the pop-up library rather than using something like the Behind Desk pickup option.

We could cobble something together with existing functionality, but the following enhancements would make the process easier:

- the ability to include an OU in the pickup library dropdown even if the OU Type is not allowed to have volumes and copies. We do not want to add copies to these locations; we just want to make them available at pickup locations. For now, we can enable the 'can have volumes and copies' flag and just rely on staff to NOT catalog items in these locations, but mistakes can happen.

- the ability to make an OU opac visible for the pickup library menu, but not for the search library selector. Once again, the OU doesn't own items and therefore shouldn't appear for search. But we do want patrons to see it in the holds pickup dropdown menu.

- The ability to add a note that displays when a specific pickup library is selected. The use case is that library staff may only be available at the senior center on Wednesday mornings to check out these holds. If that location is selected, a note should display informing the user of this fact. However, I see other good use cases for this functionality: informing the user of a temporary closing at a pickup library or alerting users of a new address if the library is in a temporary location.