Added api for custom timetable events

lib/view/pages/timetable/arbitraryAppointment.dart

@@ -0,0 +1,23 @@
+
+import '../../../api/mhsl/customTimetableEvent/customTimetableEvent.dart';
+import '../../../api/webuntis/queries/getTimetable/getTimetableResponse.dart';
+
+class ArbitraryAppointment {
+  GetTimetableResponseObject? webuntis;
+  CustomTimetableEvent? custom;
+
+  ArbitraryAppointment({this.webuntis, this.custom}) {}
+
+  bool hasWebuntis() {
+    return webuntis != null;
+  }
+
+  bool hasCustom() {
+    return custom != null;
+  }
+
+  void handlers(void Function(GetTimetableResponseObject webuntisData) webuntis, void Function(CustomTimetableEvent customData) custom) {
+    if(hasWebuntis()) webuntis(this.webuntis!);
+    if(hasCustom()) custom(this.custom!);
+  }
+}