Add Exception middleware

Shared/ExceptionDetails.cs

@@ -0,0 +1,31 @@
+using System.Text.Json;
+
+namespace Diary.Shared
+{
+	public class ExceptionDetails
+	{
+		public string? Message { get; set; }
+		public string? Title { get; set; }
+
+		public override string ToString()
+		{
+			var jsonSerializerSettings = new JsonSerializerOptions
+			{
+				PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+			};
+
+			return JsonSerializer.Serialize(this, jsonSerializerSettings);
+		}
+	}
+
+	public class ValidationExceptionDetails : ExceptionDetails
+	{
+		public List<ValidationProblemDescriptor> ModelState { get; set; } = new();
+	}
+
+	public class ValidationProblemDescriptor
+	{
+		public string? Property { get; set; }
+		public string[]? Errors { get; set; }
+	}
+}