Comment 11 for bug 1699838

Another possibility would be a single org unit setting that can take multiple values, something like:

["staff_workstation"] - always default to the staff workstation
["patron_preference", "staff_workstation"] - use the patron preference if it exists, otherwise the staff workstation
["patron_preference", "patron_home_ou"] - use the patron preference, if it exists, otherwise the patron's home library