Use id in edit-item of substitution frontend

aleksis/apps/chronos/frontend/components/calendar_feeds/details/LessonDetails.vue

@@ -252,9 +252,9 @@ export default {
     initPatchData() {
       return {
         id: this.selectedEvent.meta.id,
-        subject: this.selectedEvent.meta.subject,
-        teachers: this.selectedEvent.meta.teachers,
-        rooms: this.selectedEvent.meta.rooms,
+        subject: this.selectedEvent.meta.subject?.id,
+        teachers: this.selectedEvent.meta.teachers.map((teacher) => teacher.id),
+        rooms: this.selectedEvent.meta.rooms.map((room) => room.id),
         cancelled: this.selectedEvent.meta.cancelled,
         comment: this.selectedEvent.meta.comment,
       };