Updated comments

lib/data/models/group.dart

@@ -24,16 +24,17 @@ class Group {
     return 'Group{id: $id, name: $name, description: $description, members: $members}';
   }
 
-  /// Creates a Group instance from a JSON object (memberIds format).
+  /// Creates a Group instance from a JSON object where the related [Player]
-  /// Player objects are reconstructed from memberIds by the DataTransferService.
+  /// objects are represented by their IDs.
   Group.fromJson(Map<String, dynamic> json)
     : id = json['id'],
       createdAt = DateTime.parse(json['createdAt']),
       name = json['name'],
       description = json['description'],
-      members = []; // Populated during import via DataTransferService
+      members = [];
 
-  /// Converts the Group instance to a JSON object using normalized format (memberIds only).
+  /// Converts the Group instance to a JSON object. Related [Player] objects are
+  /// represented by their IDs.
   Map<String, dynamic> toJson() => {
     'id': id,
     'createdAt': createdAt.toIso8601String(),

lib/data/models/match.dart

@@ -38,8 +38,9 @@ class Match {
     return 'Match{id: $id, createdAt: $createdAt, endedAt: $endedAt, name: $name, game: $game, group: $group, players: $players, notes: $notes, scores: $scores, winner: $winner}';
   }
 
-  /// Creates a Match instance from a JSON object (ID references format).
+  /// Creates a Match instance from a JSON object where related objects are
-  /// Related objects are reconstructed from IDs by the DataTransferService.
+  /// represented by their IDs. Therefore, the game, group, and players are not
+  /// fully constructed here.
   Match.fromJson(Map<String, dynamic> json)
     : id = json['id'],
       createdAt = DateTime.parse(json['createdAt']),
@@ -53,13 +54,15 @@ class Match {
         description: '',
         color: GameColor.blue,
         icon: '',
-      ), // Populated during import via DataTransferService
+      ),
-      group = null, // Populated during import via DataTransferService
+      group = null,
-      players = [], // Populated during import via DataTransferService
+      players = [],
       scores = json['scores'],
       notes = json['notes'] ?? '';
 
-  /// Converts the Match instance to a JSON object using normalized format (ID references only).
+  /// Converts the Match instance to a JSON object. Related objects are
+  /// represented by their IDs, so the game, group, and players are not fully
+  /// serialized here.
   Map<String, dynamic> toJson() => {
     'id': id,
     'createdAt': createdAt.toIso8601String(),

lib/data/models/team.dart

@@ -29,7 +29,8 @@ class Team {
       createdAt = DateTime.parse(json['createdAt']),
       members = []; // Populated during import via DataTransferService
 
-  /// Converts the Team instance to a JSON object using normalized format (memberIds only).
+  /// Converts the Team instance to a JSON object. Related objects are
+  /// represented by their IDs.
   Map<String, dynamic> toJson() => {
     'id': id,
     'name': name,