ActiveStorage implements a handful of background jobs for such things as purging deleted blobs and doing analysis of uploaded images and videos. Reimplementing these to use our new model classes will be trivial, though we may wind up porting some additional functionality from Rails (since Mongoid does not currently support all of the async-job-related functionality of ActiveRecord).

In the worst case, we can implement the missing functionality in-place, rather than porting new features from Rails to Mongoid. This forms a nice way to limit the potential for scope-creep, and at the same time identify future areas of work for features we decide deserve to be ported later.