调整数据库结构，实现消息模板管理

Atomx.Admin/Atomx.Admin.Client/Models/MessageTemplateModel.cs

@@ -7,6 +7,16 @@
         /// </summary>
         public long Id { get; set; }
 
+        /// <summary>
+        /// 站点ID
+        /// </summary>
+        public long SiteId { get; set; }
+
+        /// <summary>
+        /// 语言编码
+        /// </summary>
+        public int LanguageId { get; set; }
+
         /// <summary>
         /// 消息模板类型
         /// </summary>
@@ -32,6 +42,11 @@
         /// </summary>
         public string Body { get; set; } = string.Empty;
 
+        /// <summary>
+        /// 附件文件地址列表，多个附件以逗号分隔
+        /// </summary>
+        public string Attachments { get; set; } = string.Empty;
+
         /// <summary>
         /// 是否可用
         /// </summary>