calendar error handling

car_app/lib/main.dart

@@ -80,6 +80,7 @@ class App extends StatelessWidget {
         ChangeNotifierProvider(create: (context) => CalendarViewModel(
           calendarEventService: Provider.of(context, listen: false),
           authenticationService: Provider.of(context, listen: false),
+          loggingService: Provider.of(context, listen: false),
         )),
       ],
       child: MaterialApp(

car_app/lib/viewmodel/calendar.dart

+import 'package:car_app/exception/server.dart';
 import 'package:car_app/model/calendar_event.dart';
 import 'package:car_app/model/user.dart';
 import 'package:car_app/service/interface/authentication.dart';
 import 'package:car_app/service/interface/calendar_event.dart';
+import 'package:car_app/service/interface/logging.dart';
 import 'package:flutter/foundation.dart';
 
 class CalendarViewModel extends ChangeNotifier {
   final CalendarEventService calendarEventService;
   final AuthenticationService authenticationService;
+  final LoggingService loggingService;
   final List<CalendarEvent> events = [];
 
   User? currentUser;
 
-  CalendarViewModel({required this.calendarEventService, required this.authenticationService}) {
+  CalendarViewModel({required this.calendarEventService, required this.authenticationService, required this.loggingService}) {
     authenticationService.isLoggedIn().then((isLoggedIn) async {
       if(isLoggedIn) {
         currentUser = await authenticationService.user;
       }
-    });
+    })
+    .catchError(
+      test: (e) => e is ServerException, 
+      (e, s) => loggingService.error(e.toString(), exception: e, trace: s),
+    );
   }
 
   void addNewlyAddedCalendarEvent(CalendarEvent event) {
@@ -38,7 +45,10 @@ class CalendarViewModel extends ChangeNotifier {
           _addEvent(event);
         });
       }
-    });
+    })
+    .catchError(test: (e) => e is ServerException,
+      (e, s) => loggingService.error(e.toString(), exception: e, trace: s),
+    );
   }
 
   String avatarTextFromName(String name) {
@@ -104,7 +114,11 @@ class CalendarViewModel extends ChangeNotifier {
       calendarEventService.delete(event).then((event) {
         _removeEvent(event);
         undoToast(event);
-      });
+      })
+      .catchError(
+        test: (e) => e is ServerException,
+        (e, s) => loggingService.error(e.toString(), exception: e, trace: s),
+      );
     }
   }
 
@@ -118,7 +132,14 @@ class CalendarViewModel extends ChangeNotifier {
     calendarEventService.add(event).then((eventFromServer) {
       _removeEvent(event);
       _addEvent(eventFromServer);
-    });
+    })
+    .catchError(
+      test: (e) => e is ServerException,
+      (e, s) {
+        loggingService.error(e.toString(), exception: e, trace: s);
+        _removeEvent(event);
+      },
+    );
   }
 
   bool isEventFromCurrentUser(CalendarEvent event) {