add dart client to packages

packages/dart_client/lib/src/models/read.dart

@@ -0,0 +1,31 @@
+import 'package:json_annotation/json_annotation.dart';
+
+import 'user.dart';
+
+part 'read.g.dart';
+
+/// The class that defines a read event
+@JsonSerializable()
+class Read {
+  /// Date of the read event
+  final DateTime lastRead;
+
+  /// User who sent the event
+  final User user;
+
+  /// Number of unread messages
+  final int unreadMessages;
+
+  /// Constructor used for json serialization
+  Read({
+    this.lastRead,
+    this.user,
+    this.unreadMessages,
+  });
+
+  /// Create a new instance from a json
+  factory Read.fromJson(Map<String, dynamic> json) => _$ReadFromJson(json);
+
+  /// Serialize to json
+  Map<String, dynamic> toJson() => _$ReadToJson(this);
+}