文件上传功能添加，注意使用Path.Combine处理通用路径问题（windows||docker)

CloudBuilder/CloudBuilder.Core/Policy/AppsettingsPolicy.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace CloudBuilder.Core.Policy
+{
+    public class AppsettingsPolicy
+    {
+        public const string ApplicationUrl = "ApplicationUrl";
+        public const string UrlOrigins = "UrlOrigins";
+        public const string ExcelOutputDirectory = "FileServiceSettings:ExcelOutputDirectory";
+    }
+}