(feat): Migration script for reports which are not in ES at switch over.

There are many options to handle existing reports when we toggle ES on completely.

1. We may migrate all new reports and leave all old reports and resolutions alone.
2. We can migrate ALL report data so it is queryable in ES.
3. We can lose the reports which are unresolved at the time of the switch.

I prefer one or two. Three is obviously the cheapest.