* Create new class called ApplicationIntegrationTest, so we don't have
to override ActionDispatch::IntegrationTest
* Move UI tests to inherit from ApplicationSystemTestCase
* Existing REST API or EPP tests inherit from
ApplicationIntegrationTest.
* Move `require 'application_system_test_case'` at the end of
`test_helper`
I don't particularly agree with the Rails' convention of treating UI
tests as system tests and API tests as integration tests, but I see no
benefit in actively fighting against it.
