This endpoint should serialize: the data model, settings.yaml, and all the selected Collections
The data model should only change if the user triggers a manual sync or scan (since the scheduler is turned off)
The user will need to add somewhere (probably in the admin panel):
A path (maybe we can assume it will always dump to the same path as the Metabase jar, but we probably want to let them define the path)
The collections that they want to serialize (using selective serialization).
collection_idsNon-empty, distinct array of Collection IDs
pathValid directory to serialize results to