🎨 Use feature based folder structure

lib/posts/posts_models/heatmap.dart

@@ -0,0 +1,26 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+
+part 'heatmap.freezed.dart';
+part 'heatmap.g.dart';
+
+@freezed
+sealed class SnHeatmap with _$SnHeatmap {
+  const factory SnHeatmap({
+    required String unit,
+    @JsonKey(name: 'period_start') required DateTime periodStart,
+    @JsonKey(name: 'period_end') required DateTime periodEnd,
+    required List<SnHeatmapItem> items,
+  }) = _SnHeatmap;
+
+  factory SnHeatmap.fromJson(Map<String, dynamic> json) =>
+      _$SnHeatmapFromJson(json);
+}
+
+@freezed
+sealed class SnHeatmapItem with _$SnHeatmapItem {
+  const factory SnHeatmapItem({required DateTime date, required int count}) =
+      _SnHeatmapItem;
+
+  factory SnHeatmapItem.fromJson(Map<String, dynamic> json) =>
+      _$SnHeatmapItemFromJson(json);
+}