Schema:
- add account_id to tables it was missing from
- make account_id a required column everywhere
- add [account_id] indexes, or add `account_id` to existing indices
Models:
- add `belongs_to :account` to all models (default to using a domain
model's account whenever possible)
- add account_id in all the necessary fixtures
- add account_id to insert_all hashes
- pass account_id to a few initialize calls
Miscellaneous:
- update the import script to set account_id
Note that I'm not adding account_id to the join tables primarily
because I couldn't think of an easy way to populate it without making
it a full Join model, and that was more work than I have time to take
on right now.