New: Use ASP.NET Core instead of Nancy

src/Readarr.Api.V1/Config/DownloadClientConfigController.cs

@@ -0,0 +1,19 @@
+using NzbDrone.Core.Configuration;
+using Readarr.Http;
+
+namespace Readarr.Api.V1.Config
+{
+    [V1ApiController("config/downloadclient")]
+    public class DownloadClientConfigController : ConfigController<DownloadClientConfigResource>
+    {
+        public DownloadClientConfigController(IConfigService configService)
+            : base(configService)
+        {
+        }
+
+        protected override DownloadClientConfigResource ToResource(IConfigService model)
+        {
+            return DownloadClientConfigResourceMapper.ToResource(model);
+        }
+    }
+}