function assignActivities_() {
  let ss = SpreadsheetApp.getActiveSpreadsheet();
  let activities = loadActivitySchedule_(ss);
  let activityIds = activities.map(function(activity) {
    return activity.id;
  });
  let attendees = loadAttendeeResponses_(ss, activityIds);
  assignWithRandomPriority_(attendees, activities, 2);
  writeAttendeeAssignments_(ss, attendees);
  writeActivityRosters_(ss, activities);
}
Assigns activities using a random priority/random serial dictatorship approach. The results
are then populated into two new sheets, one listing activities per person, the other listing
the rosters for each activity.

See https://en.wikipedia.org/wiki/Random_serial_dictatorship for additional information.