message: API: Add DuplicationController docs
diff: @@ -47,6 +47,9 @@ export class DuplicationController {
  * {
  * "_id": "5ab19c382ac32e46dcaa1574"
  * }
  + *
  + * @apiError NotFoundError If the course couldn't be found.
  + * @apiError ForbiddenError assertUserDuplicationAuthorization check failed.
  */
  @Post('/course/:id')
  async duplicateCourse(@Param('id') id: string,
  @@ -81,6 +84,9 @@ export class DuplicationController {
  * {
  * "_id": "5ab1a218dab93c34f8541e25"
  * }
  + *
  + * @apiError NotFoundError If the lecture or the target courseId couldn't be found.
  + * @apiError ForbiddenError assertUserDuplicationAuthorization check failed.
  */
  @Post('/lecture/:id')
  async duplicateLecture(@Param('id') id: string,
  @@ -115,6 +121,9 @@ export class DuplicationController {
  * {
  * "_id": "5ab1a380f5bbeb423070d787"
  * }
  + *
  + * @apiError NotFoundError If the unit or the target lectureId couldn't be found.
  + * @apiError ForbiddenError assertUserDuplicationAuthorization check failed.
  */
  @Post('/unit/:id')
  async duplicateUnit(@Param('id') id: string,
  