Account Sync should happen at login, 1x per day, OR on-demand (#594)

* Add last_sync_date to accounts table

* Always sync Account after Valuation or Transaction creation, update, or deletion.

Skip sync if user clicks "sync" button without changing anything

* Sync user accounts daily based on last_login_at

app/models/account/syncable.rb

@@ -14,12 +14,23 @@ module Account::Syncable
         calculator.calculate
         self.balances.upsert_all(calculator.daily_balances, unique_by: :index_account_balances_on_account_id_date_currency_unique)
         self.balances.where("date < ?", effective_start_date).delete_all
-        update!(status: "ok")
+        update!(status: "ok", last_sync_date: Date.today)
     rescue => e
         update!(status: "error")
         Rails.logger.error("Failed to sync account #{id}: #{e.message}")
     end
 
+    def can_sync?
+        # Skip account sync if account is not active or the sync process is already running
+        return false unless is_active
+        return false if syncing?
+        # If last_sync_date is blank (i.e. the account has never been synced before) allow syncing
+        return true if last_sync_date.blank?
+
+        # If last_sync_date is not today, allow syncing
+        last_sync_date != Date.today
+    end
+
     # The earliest date we can calculate a balance for
     def effective_start_date
         first_valuation_date = self.valuations.order(:date).pluck(:date).first