feat(openai): 新增反序列化回调通知事件得扩展方法

src/SKIT.FlurlHttpClient.Wechat.OpenAI/WechatOpenAIEvent.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Xml.Serialization;
+
+namespace SKIT.FlurlHttpClient.Wechat.OpenAI
+{
+    /// <summary>
+    /// 表示微信智能对话 API 回调通知事件的基类。
+    /// </summary>
+    [Serializable]
+    public class WechatOpenAIEvent
+    {
+        public static class Serialization
+        {
+            [XmlRoot("xml")]
+            public interface IXmlSerializable
+            {
+            }
+        }
+
+        /// <summary>
+        /// 获取或设置 AppId。
+        /// </summary>
+        [XmlElement("appid", IsNullable = true)]
+        public string? AppId { get; set; }
+
+        /// <summary>
+        /// 获取或设置事件类型。
+        /// </summary>
+        [XmlElement("event", IsNullable = true)]
+        public string? Event { get; set; }
+
+        /// <summary>
+        /// 获取或设置消息创建时间戳。
+        /// </summary>
+        [XmlElement("createtime", IsNullable = true)]
+        public long? CreateTimestamp { get; set; }
+    }
+}