Assign Patron default service point for requests and general customer service

Currently, when patrons request materials, the default pickup service point for the request is the first one in the dropdown menu. This means that, when patrons are creating their own requests through discovery, they need to find their preferred service point in the menu and select it each time (a minor hassle). That said, when a library staff member is creating the request on behalf or a patron, they may not even know which service point to select for the patron.

To solve this problem, new requests should auto-populate with the preferred pickup service point for the requester. It should be possible to override the default, when desired.

This feature used to be called "User branch/location" but, upon discussion with the RA SIG, the primary use of associating a patron with any type of location information would be to assign a service point as the patron’s default pick-up location for requests. Given that, we have renamed this feature "Assign Patron default pick-up service point for requests) and moved it to the Requests epic.

Current thinking on design (needs review with SIGs): https://drive.google.com/drive/folders/1lqjdblpO_3wFLYcZdR4jabGCmp0iFsmC