Plaid sync domain improvements (#2267)

Breaks our Plaid sync process out into more manageable classes. Notably, this moves the sync process to a distinct, 2-step flow:

1. Import stage - we first make API calls and import Plaid data to "mirror" tables
2. Processing stage - read the raw data, apply business rules, build internal domain models and sync balances

This provides several benefits:

- Plaid syncs can now be "replayed" without fetching API data again
- Mirror tables provide better audit and debugging capabilities
- Eliminates the "all or nothing" sync behavior that is currently in place, which is brittle

app/models/depository.rb

@@ -3,7 +3,10 @@ class Depository < ApplicationRecord
 
   SUBTYPES = {
     "checking" => { short: "Checking", long: "Checking" },
-    "savings" => { short: "Savings", long: "Savings" }
+    "savings" => { short: "Savings", long: "Savings" },
+    "hsa" => { short: "HSA", long: "Health Savings Account" },
+    "cd" => { short: "CD", long: "Certificate of Deposit" },
+    "money_market" => { short: "MM", long: "Money Market" }
   }.freeze
 
   class << self