Rails 5.2 warns:
> The `success?` predicate is deprecated and will be removed in Rails 6.0.
> Please use `successful?` as provided by Rack::Response::Helpers.
RSpec correspondingly provides `be_successful`.
Raisl 5.1 removes support for non-keyword arguments in `#process`,
`#get`, `#post`, `#patch`, `#put`, `#delete`, and `#head` for the
`ActionDispatch::IntegrationTest` and `ActionController::TestCase`
classes. This means we have to add `params` everywhere in the controller
tests.
- Drop selected_event_schedule function
- Rename scheduled_room and scheduled_start_time to room and time as if there is no selected_schedule, the event is not scheduled.
