Add Exception middleware

Shared/AppException.cs

@@ -0,0 +1,22 @@
+using System.Net;
+
+namespace Diary.Shared
+{
+	public class AppException : Exception
+	{
+		public string Title { get; }
+		public HttpStatusCode StatusCode { get; }
+
+		public AppException(HttpStatusCode statusCode, string title, string message) : base(message)
+		{
+			StatusCode = statusCode;
+			Title = title;
+		}
+
+		public AppException(HttpStatusCode statusCode, string title, string message, Exception innerException) : base(message, innerException)
+		{
+			StatusCode = statusCode;
+			Title = title;
+		}
+	}
+}