* Implement Synth as an exchange rate provider
* Add assertions to provider interface test
* Assert the correct provider error is raised
* Remove unnecessary parens
* 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
