- add tests for new address API routes
- update BUYAddress data model to include an identifier property
- add BUYAddress API tests (without stubs, WIP)

- add mocked response for test
- move error generation into BUYRequestOperation
- renamed shopify error domain constant value (ensure uniqueness)

- reduce poll iteration count
- change request URL for testing
- fix typo

- add initializer to payment provider to inject fake safari controller