Add project files.

OemanTrader.Domain/Exceptions/InvalidSymbolException.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OemanTrader.Domain.Exceptions
+{
+    public class InvalidSymbolException : Exception
+    {
+        public string Symbol { get; set; }
+        public InvalidSymbolException(string symbol)
+        {
+            Symbol = symbol;
+        }
+
+        public InvalidSymbolException(string symbol, string? message) : base(message)
+        {
+            Symbol = symbol;
+        }
+
+        public InvalidSymbolException(string symbol, string? message, Exception? innerException) : base(message, innerException)
+        {
+            Symbol = symbol;
+        }
+
+    }
+}