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_account/processor.rb

@@ -0,0 +1,99 @@
+class PlaidAccount::Processor
+  include PlaidAccount::TypeMappable
+
+  attr_reader :plaid_account
+
+  def initialize(plaid_account)
+    @plaid_account = plaid_account
+  end
+
+  # Each step represents a different Plaid API endpoint / "product"
+  #
+  # Processing the account is the first step and if it fails, we halt the entire processor
+  # Each subsequent step can fail independently, but we continue processing the rest of the steps
+  def process
+    process_account!
+    process_transactions
+    process_investments
+    process_liabilities
+  end
+
+  private
+    def family
+      plaid_account.plaid_item.family
+    end
+
+    # Shared securities reader and resolver
+    def security_resolver
+      @security_resolver ||= PlaidAccount::Investments::SecurityResolver.new(plaid_account)
+    end
+
+    def process_account!
+      PlaidAccount.transaction do
+        account = family.accounts.find_or_initialize_by(
+          plaid_account_id: plaid_account.id
+        )
+
+        # Name and subtype are the only attributes a user can override for Plaid accounts
+        account.enrich_attributes(
+          {
+            name: plaid_account.name,
+            subtype: map_subtype(plaid_account.plaid_type, plaid_account.plaid_subtype)
+          },
+          source: "plaid"
+        )
+
+        account.assign_attributes(
+          accountable: map_accountable(plaid_account.plaid_type),
+          balance: balance_calculator.balance,
+          currency: plaid_account.currency,
+          cash_balance: balance_calculator.cash_balance
+        )
+
+        account.save!
+      end
+    end
+
+    def process_transactions
+      PlaidAccount::Transactions::Processor.new(plaid_account).process
+    rescue => e
+      report_exception(e)
+    end
+
+    def process_investments
+      PlaidAccount::Investments::TransactionsProcessor.new(plaid_account, security_resolver: security_resolver).process
+      PlaidAccount::Investments::HoldingsProcessor.new(plaid_account, security_resolver: security_resolver).process
+    rescue => e
+      report_exception(e)
+    end
+
+    def process_liabilities
+      case [ plaid_account.plaid_type, plaid_account.plaid_subtype ]
+      when [ "credit", "credit card" ]
+        PlaidAccount::Liabilities::CreditProcessor.new(plaid_account).process
+      when [ "loan", "mortgage" ]
+        PlaidAccount::Liabilities::MortgageProcessor.new(plaid_account).process
+      when [ "loan", "student" ]
+        PlaidAccount::Liabilities::StudentLoanProcessor.new(plaid_account).process
+      end
+    rescue => e
+      report_exception(e)
+    end
+
+    def balance_calculator
+      if plaid_account.plaid_type == "investment"
+        @balance_calculator ||= PlaidAccount::Investments::BalanceCalculator.new(plaid_account, security_resolver: security_resolver)
+      else
+        OpenStruct.new(
+          balance: plaid_account.current_balance || plaid_account.available_balance,
+          cash_balance: plaid_account.available_balance || 0
+        )
+      end
+    end
+
+    def report_exception(error)
+      Sentry.capture_exception(error) do |scope|
+        scope.set_tags(plaid_account_id: plaid_account.id)
+      end
+    end
+end