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

test/controllers/pages_controller_test.rb

@@ -2,7 +2,7 @@ require "test_helper"
 
 class PagesControllerTest < ActionDispatch::IntegrationTest
   setup do
-    sign_in users(:family_admin)
+    sign_in @user = users(:family_admin)
   end
 
   test "dashboard" do