The following changes effect anyone who creates a plugin or theme for one of the applications, or wishes to integrate with the application through the REST API.
Review assignments were refactored according to the Repository pattern, e.g., to get an assignment by ID use:
$reviewAssignment = Repo::reviewAssignments()->get($id)
ReviewAssignmentDAO was removed
Backend Submissions Handler was extended to support dashboards views - submissions and review assignments lists
See all the changes in 3.5 API Reference