message: Restore original lecture duplication code
diff: @@ -79,13 +79,14 @@ lectureSchema.statics.importJSON = async function(lecture: ILecture, courseId: s
  try {
  const savedLecture = await new Lecture(lecture).save();
  - savedLecture.units = await Unit.create(units);
  - await savedLecture.save();
  const course = await Course.findById(courseId);
  course.lectures.push(savedLecture);
  await course.save();
  + for (const unit of units) {
  + await Unit.schema.statics.importJSON(unit, courseId, savedLecture._id);
  + }
  const newLecture: ILectureModel = await Lecture.findById(savedLecture._id);
  return newLecture.toObject();
  