added persisted app settings

lib/model/settings.dart

@@ -2,28 +2,38 @@ import '../assets/constants.dart' as constants;
 
 class Settings {
   final String exportDirectoryPath;
+  final bool alwaysExportEnabled;
 
-  Settings._({required this.exportDirectoryPath});
+  Settings._({
+    required this.exportDirectoryPath,
+    required this.alwaysExportEnabled,
+  });
 
   Map<String, dynamic> toJson() {
-    return {'exportDirectoryPath': exportDirectoryPath};
+    return {
+      'exportDirectoryPath': exportDirectoryPath,
+      'alwaysExportEnabled': alwaysExportEnabled,
+    };
   }
 
   factory Settings.fromJson(Map<String, dynamic> json) {
     return Settings._(
       exportDirectoryPath: json['exportDirectoryPath'] as String,
+      alwaysExportEnabled: json['alwaysExportEnabled'] as bool,
     );
   }
 
   factory Settings.defaults() {
     return Settings._(
       exportDirectoryPath: constants.defaultAndroidExportDirectory,
+      alwaysExportEnabled: false,
     );
   }
 
-  Settings copyWith({String? exportDirectoryPath}) {
+  Settings copyWith({String? exportDirectoryPath, bool? alwaysExportEnabled}) {
     return Settings._(
       exportDirectoryPath: exportDirectoryPath ?? this.exportDirectoryPath,
+      alwaysExportEnabled: alwaysExportEnabled ?? this.alwaysExportEnabled,
     );
   }
 }