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/plaid_item/accounts_snapshot.rb

@@ -0,0 +1,79 @@
+# All Plaid data is fetched at the item-level.  This class is a simple wrapper that
+# providers a convenience method, get_account_data which scopes the item-level payload
+# to each Plaid Account
+class PlaidItem::AccountsSnapshot
+  def initialize(plaid_item, plaid_provider:)
+    @plaid_item = plaid_item
+    @plaid_provider = plaid_provider
+  end
+
+  def accounts
+    @accounts ||= plaid_provider.get_item_accounts(plaid_item.access_token).accounts
+  end
+
+  def get_account_data(account_id)
+    AccountData.new(
+      account_data: accounts.find { |a| a.account_id == account_id },
+      transactions_data: account_scoped_transactions_data(account_id),
+      investments_data: account_scoped_investments_data(account_id),
+      liabilities_data: account_scoped_liabilities_data(account_id)
+    )
+  end
+
+  private
+    attr_reader :plaid_item, :plaid_provider
+
+    TransactionsData = Data.define(:added, :modified, :removed)
+    LiabilitiesData = Data.define(:credit, :mortgage, :student)
+    InvestmentsData = Data.define(:transactions, :holdings, :securities)
+    AccountData = Data.define(:account_data, :transactions_data, :investments_data, :liabilities_data)
+
+    def account_scoped_transactions_data(account_id)
+      return nil unless transactions_data
+
+      TransactionsData.new(
+        added: transactions_data.added.select { |t| t.account_id == account_id },
+        modified: transactions_data.modified.select { |t| t.account_id == account_id },
+        removed: transactions_data.removed.select { |t| t.account_id == account_id }
+      )
+    end
+
+    def account_scoped_investments_data(account_id)
+      return nil unless investments_data
+
+      transactions = investments_data.transactions.select { |t| t.account_id == account_id }
+      holdings = investments_data.holdings.select { |h| h.account_id == account_id }
+      securities = transactions.count > 0 && holdings.count > 0 ? investments_data.securities : []
+
+      InvestmentsData.new(
+        transactions: transactions,
+        holdings: holdings,
+        securities: securities
+      )
+    end
+
+    def account_scoped_liabilities_data(account_id)
+      return nil unless liabilities_data
+
+      LiabilitiesData.new(
+        credit: liabilities_data.credit&.find { |c| c.account_id == account_id },
+        mortgage: liabilities_data.mortgage&.find { |m| m.account_id == account_id },
+        student: liabilities_data.student&.find { |s| s.account_id == account_id }
+      )
+    end
+
+    def transactions_data
+      return nil unless plaid_item.supports_product?("transactions")
+      @transactions_data ||= plaid_provider.get_transactions(plaid_item.access_token)
+    end
+
+    def investments_data
+      return nil unless plaid_item.supports_product?("investments")
+      @investments_data ||= plaid_provider.get_item_investments(plaid_item.access_token)
+    end
+
+    def liabilities_data
+      return nil unless plaid_item.supports_product?("liabilities")
+      @liabilities_data ||= plaid_provider.get_item_liabilities(plaid_item.access_token)
+    end
+end