feat:增加消息记录功能

lib/models/chat_message.g.dart

@@ -0,0 +1,24 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'chat_message.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+ChatMessage _$ChatMessageFromJson(Map<String, dynamic> json) => ChatMessage(
+  msgId: (json['msgId'] as num).toInt(),
+  senderId: (json['senderId'] as num).toInt(),
+  content: json['content'] as String,
+  msgType: (json['msgType'] as num).toInt(),
+  createTime: DateTime.parse(json['createTime'] as String),
+);
+
+Map<String, dynamic> _$ChatMessageToJson(ChatMessage instance) =>
+    <String, dynamic>{
+      'msgId': instance.msgId,
+      'senderId': instance.senderId,
+      'content': instance.content,
+      'msgType': instance.msgType,
+      'createTime': instance.createTime.toIso8601String(),
+    };