TF-138 Add domain layer for search mail with text pattern

lib/features/thread/domain/model/search_query.dart

@@ -0,0 +1,11 @@
+
+import 'package:equatable/equatable.dart';
+
+class SearchQuery with EquatableMixin {
+  final String value;
+
+  SearchQuery(this.value);
+
+  @override
+  List<Object?> get props => [value];
+}