Assignees who have marked the assignment complete on their side.
OptionalpracticedOptional total practice minutes from an external aggregator (e.g. a
server-side PracticeLog). Counts as activity for the in_progress
branch even when userActivities is empty — useful for apps that
keep practice time outside the assignment file.
Per-user activity records. Any non-empty entry counts as activity.
All assignees of the assignment.