TF-3985 Prefer to use domain from platform rather than from email

lib/features/mailbox_dashboard/presentation/extensions/handle_paywall_extension.dart

@@ -4,6 +4,7 @@ import 'package:tmail_ui_user/features/paywall/domain/model/paywall_url_pattern.
 import 'package:tmail_ui_user/features/paywall/domain/usecases/get_paywall_url_interactor.dart';
 import 'package:tmail_ui_user/main/localizations/app_localizations.dart';
 import 'package:tmail_ui_user/main/routes/route_navigation.dart';
+import 'package:tmail_ui_user/main/routes/route_utils.dart';
 import 'package:tmail_ui_user/main/utils/app_utils.dart';
 
 extension ValidateSaasPremiumAvailableExtension on MailboxDashBoardController {
@@ -43,6 +44,7 @@ extension ValidateSaasPremiumAvailableExtension on MailboxDashBoardController {
 
     final qualifiedPaywall = paywallUrlPattern!.getQualifiedUrl(
       ownerEmail: ownEmailAddress.value,
+      domainName: RouteUtils.getRootDomain(),
     );
 
     AppUtils.launchLink(qualifiedPaywall);

lib/features/paywall/domain/model/paywall_url_pattern.dart

@@ -14,7 +14,7 @@ class PaywallUrlPattern with EquatableMixin {
     return PaywallUtils.buildPaywallUrlFromTemplate(
       template: pattern,
       localPart: mailAddress?.localPart,
-      domainName: mailAddress?.domain.domainName,
+      domainName: domainName ?? mailAddress?.domain.domainName,
     );
   }
 

lib/main/routes/route_utils.dart

@@ -264,4 +264,20 @@ abstract class RouteUtils {
   static String generateMailtoLink(String mailAddress) {
     return '$baseOriginUrl/$mailtoPrefix/?uri=$mailtoPrefix:$mailAddress';
   }
+
+  static String? getRootDomain({String? hostname}) {
+    final host = hostname ?? html.window.location.hostname;
+
+    if (host == null || host.isEmpty) {
+      return null;
+    }
+
+    final parts = host.split('.');
+
+    if (parts.length >= 2) {
+      return '${parts[parts.length - 2]}.${parts.last}';
+    }
+
+    return host;
+  }
 }