We're currently using AASM, a status enum, and a handful of timestamp columns (e.g. archived_at) to manage the state of an invoice. This is too much!

Here's what we need to do.

1. Fully build out the AASM states for Invoice so that it can handle all states
2. Write a migration script that will update aasm_state with the correct state. It will become the one source of truth
3. Remove the status enum and clean up unused or old scopes and state-related methods

warning: this is a fairly difficult ticket! take it on if you're looking for a challenge