cka-y

Tasks: - [x] Add `location_groups.txt` schema - [ ] Update `stop_times.txt` schema - [x] Modify `stop_id` from required to conditionally required - [x] Add `location_group_id` - [ ] Add `location_id`...

Blocked until #1750 is completed

Closing this as the issue is not reproducible. I was able to observe the foreign key error notice for the specified example feed and trip ID.