Refactor

lib/core/utils/json_converters.dart

@@ -0,0 +1,11 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+class IntervalInSecondsConverter implements JsonConverter<Duration, int> {
+  const IntervalInSecondsConverter();
+
+  @override
+  Duration fromJson(int json) => Duration(seconds: json);
+
+  @override
+  int toJson(Duration object) => object.inSeconds;
+}