Multi-Currency Part 2 (#543)

* Support all currencies, handle outside DB

* Remove currencies from seed

* Fix account balance namespace

* Set default currency on authentication

* Cache currency instances

* Implement multi-currency syncs with tests

* Series fallback, passing tests

* Fix conflicts

* Make value group concrete class that works with currency values

* Fix migration conflict

* Update tests to expect multi-currency results

* Update account list to use group method

* Namespace updates

* Fetch unknown exchange rates from API

* Fix date range bug

* Ensure demo data works without external API

* Enforce cascades only at DB level

db/migrate/20240308121431_remove_currency_table.rb

@@ -0,0 +1,5 @@
+class RemoveCurrencyTable < ActiveRecord::Migration[7.2]
+  def change
+    drop_table :currencies
+  end
+end

db/migrate/20240313141813_update_unique_indexes_for_account_balance_and_exchange_rate.rb

@@ -0,0 +1,7 @@
+class UpdateUniqueIndexesForAccountBalanceAndExchangeRate < ActiveRecord::Migration[7.2]
+  def change
+    rename_index :exchange_rates, 'idx_on_base_currency_converted_currency_date_255be792be', 'index_exchange_rates_on_base_converted_date_unique'
+    remove_index :account_balances, name: "index_account_balances_on_account_id_and_date"
+    add_index :account_balances, [ :account_id, :date, :currency ], unique: true, name: "index_account_balances_on_account_id_date_currency_unique"
+  end
+end

db/migrate/20240313203622_remove_converted_balance_from_account.rb

@@ -0,0 +1,6 @@
+class RemoveConvertedBalanceFromAccount < ActiveRecord::Migration[7.2]
+  def change
+    remove_column :accounts, :converted_balance, :decimal
+    remove_column :accounts, :converted_currency, :string
+  end
+end