Fix adding message token error when creating new account

- Set an empty token field and update the field 1 second later
- A quick and dirty solution that works after delaying the update by 1 second

lib/data/user/repositories/user_repository.dart

@@ -19,13 +19,25 @@ class UserRepository {
   String get displayName => FirebaseAuth.instance.currentUser.displayName;
 
   Future<void> saveToken(String token) async {
-    await _userDoc.update({
+    await _userDoc.set({
       'tokens': FieldValue.arrayUnion([token]),
+    }, SetOptions(merge: true));
+    // Quick and dirty solution, it just works.
+    Future.delayed(Duration(seconds: 1), () {
+      _userDoc.update({
+        'tokens': FieldValue.arrayUnion([token]),
+      });
     });
   }
 
-  Future<void> update(AppUser appUser) async {
-    await _userDoc.update(appUser.toMap());
+  Future<void> deleteToken(String token) {
+    return _userDoc.update({
+      'tokens': FieldValue.arrayRemove([token]),
+    });
+  }
+
+  Future<void> update(AppUser appUser) {
+    return _userDoc.update(appUser.toMap());
   }
 
   Future<void> delete() => _userDoc.delete();

lib/ui/profile/user_profile_page.dart

@@ -3,6 +3,7 @@ import 'package:farmassist/bloc/authentication/authentication.dart';
 import 'package:farmassist/ui/profile/avatar.dart';
 import 'package:farmassist/ui/profile/user_info_field.dart';
 import 'package:farmassist/ui/widgets/tab_page.dart';
+import 'package:farmassist/utils/message_handler.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
@@ -51,9 +52,12 @@ class _LogOutButton extends StatelessWidget {
               borderRadius: BorderRadius.circular(30.0),
             ),
             color: const Color(0xFFFFD600),
-            onPressed: () => context
-                .read<AuthenticationBloc>()
-                .add(AuthenticationLogoutRequested()),
+            onPressed: () async {
+              await context.read<MessageHandler>().deleteToken();
+              context
+                  .read<AuthenticationBloc>()
+                  .add(AuthenticationLogoutRequested());
+            },
           ),
         ),
       ),

lib/utils/message_handler.dart

@@ -9,10 +9,15 @@ class MessageHandler {
 
   FirebaseMessaging _messaging;
   UserRepository _userRepository;
+  String _token;
 
   Future<void> generateToken() async {
-    String token = await _messaging.getToken();
-    await _userRepository.saveToken(token);
+    _token = await _messaging.getToken();
+    await _userRepository.saveToken(_token);
     _messaging.onTokenRefresh.listen(_userRepository.saveToken);
   }
+
+  Future<void> deleteToken() {
+    return _userRepository.deleteToken(_token);
+  }
 }