message: API: checkPrivileges of /api/export/lecture/:id
diff: @@ -68,7 +68,11 @@ export class ExportController {
  * }
  */
  @Get('/lecture/:id')
  - async exportLecture(@Param('id') id: string) {
  + async exportLecture(@Param('id') id: string, @CurrentUser() currentUser: IUser) {
  + const course = await Course.findOne({lectures: id});
  + if (!course.checkPrivileges(currentUser).userCanEditCourse) {
  + throw new ForbiddenError();
  + }
  const lecture = await Lecture.findById(id);
  return lecture.exportJSON();
  }
  