Allow for selection from among multiple reading rooms

[ctgraham]

Is your feature request related to a problem? Please describe.

Institutions may have multiple reading rooms available to the public. Currently, there is no way to indicate the reading room of interest in the Appointment Request, outside of adding a comment.

Describe the solution you'd like

Pull Reading Room information via API from Aeon into a cache available to DIMES. If more than one Reading Room exists, present a new UI element for the researcher to select in the ReadingRoomRequestModal form. This UI element is a dropdown is a selector of the possible reading rooms.

Describe alternatives you've considered

Our initial implementation hardcoded the reading rooms, and an easy transition might be to make these just a configuration item in DIMES, rather than an API call to Aeon. The API call to Aeon does, however, start to get us thinking in that direction, which might be helpful for other things, like limiting hours availability to those published in Aeon, or creating Appointments within Aeon.

Additional context

Danger Zone: Reading Rooms might have different hours per location, so implementing this along with a datetime picker might introduce expectations that these two controls be related, and further related to Aeon's Appointment system. The way that Aeon does this in their own UI is a bit painful, and we don't want to necessarily follow their example.

This issue relates to RockefellerArchiveCenter/request_broker#227