Ability to export and import settings configurations in OA Admin

Develop support for exporting and importing OpenAthens Admin settings via XML file.

Use case #1: Onboarding

When setting up a new library, upload a file of their customizations and preferences so that less manual work (e.g. clicking, typing, searching) will be required in the UI of OA Admin.

Example: Onboarding team uploads a configuration file that instantly applies the customer's preferences to all settings and allocates all necessary resources in the catalogue. This accomplishes a ton of work on Day 1 of the onboarding, especially for libraries with lots of resources to allocate in the OA catalogue.

Use case #2: Emergency Response

When an administrator inadvertently causes an OpenAthens outage by changing vital settings in OA Admin, upload a recent configuration file to revert settings back to how they were before the outage.

Example: Download all the settings of a local authentication connector (metadata, attribute mappings, permission rules). That way, if an administrator accidentally deletes a "live" Azure connector, they can quickly restore it by uploading a previously-saved export of that connector. Or if an administrator accidentally deletes their Default Permission Set, they could quickly add it back by uploading a saved copy from before.