refactor: Enable more lints

lib/utils/background_push.dart

@@ -300,13 +300,13 @@ class BackgroundPush {
     }
 
     // initialise the plugin. app_icon needs to be a added as a drawable resource to the Android head project
-    var initializationSettingsAndroid =
+    final initializationSettingsAndroid =
         AndroidInitializationSettings('notifications_icon');
-    var initializationSettingsIOS =
+    final initializationSettingsIOS =
         IOSInitializationSettings(onDidReceiveLocalNotification: (i, a, b, c) {
       return null;
     });
-    var initializationSettings = InitializationSettings(
+    final initializationSettings = InitializationSettings(
       android: initializationSettingsAndroid,
       iOS: initializationSettingsIOS,
     );
@@ -622,7 +622,7 @@ class BackgroundPush {
     );
 
     // Show notification
-    var androidPlatformChannelSpecifics = _getAndroidNotificationDetails(
+    final androidPlatformChannelSpecifics = _getAndroidNotificationDetails(
       styleInformation: MessagingStyleInformation(
         person,
         conversationTitle: title,
@@ -636,8 +636,8 @@ class BackgroundPush {
       ),
       ticker: l10n.newMessageInFluffyChat,
     );
-    var iOSPlatformChannelSpecifics = IOSNotificationDetails();
-    var platformChannelSpecifics = NotificationDetails(
+    final iOSPlatformChannelSpecifics = IOSNotificationDetails();
+    final platformChannelSpecifics = NotificationDetails(
       android: androidPlatformChannelSpecifics,
       iOS: iOSPlatformChannelSpecifics,
     );
@@ -655,8 +655,8 @@ class BackgroundPush {
       await setupLocalNotificationsPlugin();
 
       await loadLocale();
-      String eventId = data['event_id'];
-      String roomId = data['room_id'];
+      final String eventId = data['event_id'];
+      final String roomId = data['room_id'];
       final unread = ((data['counts'] is String
               ? json.decode(data.tryGet<String>('counts', '{}'))
               : data.tryGet<Map<String, dynamic>>(
@@ -668,9 +668,9 @@ class BackgroundPush {
       }
 
       // Display notification
-      var androidPlatformChannelSpecifics = _getAndroidNotificationDetails();
-      var iOSPlatformChannelSpecifics = IOSNotificationDetails();
-      var platformChannelSpecifics = NotificationDetails(
+      final androidPlatformChannelSpecifics = _getAndroidNotificationDetails();
+      final iOSPlatformChannelSpecifics = IOSNotificationDetails();
+      final platformChannelSpecifics = NotificationDetails(
         android: androidPlatformChannelSpecifics,
         iOS: iOSPlatformChannelSpecifics,
       );
@@ -692,20 +692,20 @@ class BackgroundPush {
     final thumbnail = width == null && height == null ? false : true;
     final tempDirectory = (await getTemporaryDirectory()).path;
     final prefix = thumbnail ? 'thumbnail' : '';
-    var file =
+    final file =
         File('$tempDirectory/${prefix}_${content.toString().split("/").last}');
 
     if (!file.existsSync()) {
       final url = thumbnail
           ? content.getThumbnail(client, width: width, height: height)
           : content.getDownloadLink(client);
-      var request = await HttpClient().getUrl(Uri.parse(url));
-      var response = await request.close();
+      final request = await HttpClient().getUrl(Uri.parse(url));
+      final response = await request.close();
       if (response.statusCode >= 300) {
         // we are not in the 2xx range
         return null;
       }
-      var bytes = await consolidateHttpClientResponseBytes(response);
+      final bytes = await consolidateHttpClientResponseBytes(response);
       await file.writeAsBytes(bytes);
     }
 

lib/utils/date_time_extension.dart

@@ -44,13 +44,13 @@ extension DateTimeExtension on DateTime {
   /// Returns [localizedTimeOfDay()] if the ChatTime is today, the name of the week
   /// day if the ChatTime is this week and a date string else.
   String localizedTimeShort(BuildContext context) {
-    var now = DateTime.now();
+    final now = DateTime.now();
 
-    var sameYear = now.year == year;
+    final sameYear = now.year == year;
 
-    var sameDay = sameYear && now.month == month && now.day == day;
+    final sameDay = sameYear && now.month == month && now.day == day;
 
-    var sameWeek = sameYear &&
+    final sameWeek = sameYear &&
         !sameDay &&
         now.millisecondsSinceEpoch - millisecondsSinceEpoch <
             1000 * 60 * 60 * 24 * 7;
@@ -86,11 +86,11 @@ extension DateTimeExtension on DateTime {
   /// shows the date.
   /// TODO: Add localization
   String localizedTime(BuildContext context) {
-    var now = DateTime.now();
+    final now = DateTime.now();
 
-    var sameYear = now.year == year;
+    final sameYear = now.year == year;
 
-    var sameDay = sameYear && now.month == month && now.day == day;
+    final sameDay = sameYear && now.month == month && now.day == day;
 
     if (sameDay) return localizedTimeOfDay(context);
     return L10n.of(context).dateAndTimeOfDay(

lib/utils/matrix_file_extension.dart

@@ -15,7 +15,7 @@ extension MatrixFileExtension on MatrixFile {
     if (kIsWeb) {
       final fileName = name.split('/').last;
       final mimeType = mime(fileName);
-      var element = html.document.createElement('a');
+      final element = html.document.createElement('a');
       element.setAttribute(
           'href', html.Url.createObjectUrlFromBlob(html.Blob([bytes])));
       element.setAttribute('target', '_blank');

lib/utils/platform_infos.dart

@@ -40,7 +40,7 @@ abstract class PlatformInfos {
   }
 
   static void showDialog(BuildContext context) async {
-    var version = await PlatformInfos.getVersion();
+    final version = await PlatformInfos.getVersion();
     showAboutDialog(
       context: context,
       useRootNavigator: false,

lib/utils/room_status_extension.dart

@@ -35,7 +35,7 @@ extension RoomStatusExtension on Room {
 
   String getLocalizedTypingText(BuildContext context) {
     var typingText = '';
-    var typingUsers = this.typingUsers;
+    final typingUsers = this.typingUsers;
     typingUsers.removeWhere((User u) => u.id == client.userID);
 
     if (AppConfig.hideTypingUsernames) {

lib/utils/url_launcher.dart

@@ -40,7 +40,7 @@ class UrlLauncher {
       var roomId = room?.id;
       // we make the servers a set and later on convert to a list, so that we can easily
       // deduplicate servers added via alias lookup and query parameter
-      var servers = <String>{};
+      final servers = <String>{};
       if (room == null && roomIdOrAlias.sigil == '#') {
         // we were unable to find the room locally...so resolve it
         final response = await showFutureLoadingDialog(