Feature request ✨

Currently, we when add students to an existing Roster, we do it within the request-response cycle. So if someone uploads a large .csv file or adds a large list of students, it takes a long time for the upload to happen. Also if there's a timeout or an error in adding those entries, we rollback all of them, which also takes a lot of time.

Moving this process to a background job would be a much better UX for the user and also reduce response times.

The steps involved in doing so would be:

1. Move .create_entries to a background job.
2. Setup ActionCable channel for sending progress report to the user.
3. Handle invalid entries.

In the first iteration, we could move the process to a background job and just send a flash message on the lines of "We are adding students to your roster, please check in sometime".

And in the future iterations we can add the ActionCable support.

cc: @andrewbredow @d12