Additional cache columns on balances for activity view breakdowns (#2505)

* Initial schema iteration

* Add new balance components

* Add existing data migrator to backfill components

* Update calculator test assertions for new balance components

* Update flow assertions for forward calculator

* Update reverse calculator flows assumptions

* Forward calculator tests passing

* Get all calculator tests passing

* Assert flows factor

app/data_migrations/balance_component_migrator.rb

@@ -0,0 +1,59 @@
+class BalanceComponentMigrator
+  def self.run
+    ActiveRecord::Base.transaction do
+      # Step 1: Update flows factor
+      ActiveRecord::Base.connection.execute <<~SQL
+        UPDATE balances SET
+          flows_factor = CASE WHEN a.classification = 'asset' THEN 1 ELSE -1 END
+        FROM accounts a
+        WHERE a.id = balances.account_id
+      SQL
+
+      # Step 2: Set start values using LOCF (Last Observation Carried Forward)
+      ActiveRecord::Base.connection.execute <<~SQL
+        UPDATE balances b1
+        SET
+          start_cash_balance = COALESCE(prev.cash_balance, 0),
+          start_non_cash_balance = COALESCE(prev.balance - prev.cash_balance, 0)
+        FROM balances b1_inner
+        LEFT JOIN LATERAL (
+          SELECT
+            b2.cash_balance,
+            b2.balance
+          FROM balances b2
+          WHERE b2.account_id = b1_inner.account_id
+          AND b2.currency = b1_inner.currency
+          AND b2.date < b1_inner.date
+          ORDER BY b2.date DESC
+          LIMIT 1
+        ) prev ON true
+        WHERE b1.id = b1_inner.id
+      SQL
+
+      # Step 3: Calculate net inflows
+      # A slight workaround to the fact that we can't easily derive inflows/outflows from our current data model, and
+      # the tradeoff not worth it since each new sync will fix it. So instead, we sum up *net* flows, and throw the signed
+      # amount in the "inflows" column, and zero-out the "outflows" column so our math works correctly with incomplete data.
+      ActiveRecord::Base.connection.execute <<~SQL
+        UPDATE balances SET
+          cash_inflows = (cash_balance - start_cash_balance) * flows_factor,
+          cash_outflows = 0,
+          non_cash_inflows = ((balance - cash_balance) - start_non_cash_balance) * flows_factor,
+          non_cash_outflows = 0,
+          net_market_flows = 0
+      SQL
+
+      # Verify data integrity
+      # All end_balance values should match the original balance
+      invalid_count = ActiveRecord::Base.connection.select_value(<<~SQL)
+        SELECT COUNT(*)
+        FROM balances b
+        WHERE ABS(b.balance - b.end_balance) > 0.0001
+      SQL
+
+      if invalid_count > 0
+        raise "Data migration failed validation: #{invalid_count} balances have incorrect end_balance values"
+      end
+    end
+  end
+end