Standardize HTML sanitizing when preview email (#3223)

lib/features/base/upgradeable/upgrade_hive_database_steps_v12.dart

@@ -0,0 +1,17 @@
+
+import 'package:tmail_ui_user/features/base/upgradeable/upgrade_database_steps.dart';
+import 'package:tmail_ui_user/features/caching/caching_manager.dart';
+
+class UpgradeHiveDatabaseStepsV12 extends UpgradeDatabaseSteps {
+
+  final CachingManager _cachingManager;
+
+  UpgradeHiveDatabaseStepsV12(this._cachingManager);
+
+  @override
+  Future<void> onUpgrade(int oldVersion, int newVersion) async {
+    if (oldVersion > 0 && oldVersion < newVersion && newVersion == 12) {
+      await _cachingManager.clearEmailCacheAndAllStateCache();
+    }
+  }
+}