chore(tenpayv3): 新增基于 .NET Framework 4.7 的示例项目

samples/SKIT.FlurlHttpClient.Wechat.TenpayV3.Sample_NetFramework47/Services/BackgroundJobs/TenpayCertificateRefreshingBackgroundJob.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Diagnostics;
+using System.Threading.Tasks;
+
+namespace SKIT.FlurlHttpClient.Wechat.TenpayV3.Sample.Services.BackgroundJobs
+{
+    using SKIT.FlurlHttpClient.Wechat.TenpayV3.Models;
+    using SKIT.FlurlHttpClient.Wechat.TenpayV3.Settings;
+
+    class TenpayCertificateRefreshingBackgroundJob
+    {
+        private readonly HttpClients.IWechatTenpayHttpClientFactory _tenpayHttpClientFactory;
+
+        public TenpayCertificateRefreshingBackgroundJob(
+            HttpClients.IWechatTenpayHttpClientFactory tenpayHttpClientFactory)
+        {
+            _tenpayHttpClientFactory = tenpayHttpClientFactory;
+        }
+
+        public async Task ExecuteAsync()
+        {
+            foreach (var tenpayMerchantOptions in Options.TenpayOptions.Instance.Value.Merchants)
+            {
+                try
+                {
+                    var client = _tenpayHttpClientFactory.Create(tenpayMerchantOptions.MerchantId);
+                    var request = new QueryCertificatesRequest();
+                    var response = await client.ExecuteQueryCertificatesAsync(request);
+                    if (response.IsSuccessful())
+                    {
+                        // NOTICE:
+                        //   如果启用了 `AutoDecryptResponseSensitiveProperty` 配置项，则无需再手动执行下面被注释的解密方法：
+                        //   response = client.DecryptResponseSensitiveProperty(response);
+
+                        foreach (var certificateModel in response.CertificateList)
+                        {
+                            client.CertificateManager.AddEntry(new CertificateEntry(certificateModel));
+                        }
+
+                        Debug.WriteLine("刷新微信商户平台证书成功。");
+                    }
+                    else
+                    {
+                        Debug.WriteLine(
+                            "刷新微信商户平台证书失败（状态码：{0}，错误代码：{1}，错误描述：{2}）。",
+                            response.RawStatus, response.ErrorCode, response.ErrorMessage
+                        );
+                    }
+                }
+                catch (Exception ex)
+                {
+                    Debug.WriteLine("刷新微信商户平台证书遇到异常。\r\n{0}", ex);
+                }
+            }
+        }
+    }
+}