TF-1362: [Data] Implement store and get LastTimeDismissedSpamReport in repository and datasource

lib/features/mailbox_dashboard/domain/model/spam_report.dart

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