Create the new ingester for dashboard_db

One of the ideas for inserting data into the new db is to keep checking in the submission folder/spool for changes and convert from json to django model, which will allow for data insertion.

- [x] Reuse some of the existing ingester
- [x] #1369
- [x] #1379
- [ ] #1376
- [x] #1373

Start by reviewing the existing ingester and the submission folder/spool workflow; no files or tests are named in the issue. Determine how JSON submissions should be converted to Django models and inserted into dashboard_db, then verify that changes in the spool are detected and stored correctly.

Written by the indexing model from the issue text.