Effective API changes:
- nil serializes to null, not empty string
- dates serialize to IETF RFC 3339 with millisecond precision, not
second precision surrounded by spaces
EventSchedule start time should be in hours range of the conference.Therefore it adds validation on start_time attribute of event schedule model. It also adds test for the same.
- 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.
