Add TimelineGroupingListdata parsing of type

lib/models/timeline_grouping_list_data.dart

@@ -1,16 +1,26 @@
+enum GroupingType {
+  channel,
+  circle,
+  group,
+}
+
 class TimelineGroupingListData {
-  static final followersPseudoCircle =
-      TimelineGroupingListData('~', 'Followers');
+  static const followersPseudoCircle =
+      TimelineGroupingListData('~', 'Followers', GroupingType.circle);
+
+  static const empty = TimelineGroupingListData('', '', GroupingType.circle);
 
   final String id;
 
   final String name;
 
-  TimelineGroupingListData(this.id, this.name);
+  final GroupingType groupingType;
+
+  const TimelineGroupingListData(this.id, this.name, this.groupingType);
 
   @override
   String toString() {
-    return 'CircleData{id: $id, name: $name}';
+    return 'CircleData{id: $id, name: $name, type: ${groupingType.name}}';
   }
 
   @override

lib/serializers/mastodon/timeline_grouping_list_data.dart

@@ -2,9 +2,26 @@ import '../../models/timeline_grouping_list_data.dart';
 
 extension TimelineGroupingListDataMastodonExtensions
     on TimelineGroupingListData {
-  static TimelineGroupingListData fromJson(Map<String, dynamic> json) =>
-      TimelineGroupingListData(
-        json['id'],
-        json['title'],
-      );
+  static TimelineGroupingListData fromJson(Map<String, dynamic> json) {
+    final id = json['id']?.toString() ?? '';
+    final typeString = json['replies_policy']?.toString() ?? '';
+
+    late final GroupingType type;
+    if (typeString == 'followed') {
+      if (id.startsWith('channel')) {
+        type = GroupingType.channel;
+      } else if (id.startsWith('group')) {
+        type = GroupingType.group;
+      } else {
+        type = GroupingType.circle;
+      }
+    } else {
+      type = GroupingType.circle;
+    }
+    return TimelineGroupingListData(
+      id,
+      json['title'],
+      type,
+    );
+  }
 }