Добавил домен

backend/UniVerse.Domain/Exceptions/NotFoundException.cs

@@ -0,0 +1,13 @@
+namespace UniVerse.Domain.Exceptions;
+
+public class NotFoundException : Exception
+{
+    public NotFoundException(string entityName, object key)
+        : base($"{entityName} with key '{key}' was not found.")
+    {
+    }
+
+    public NotFoundException(string message) : base(message)
+    {
+    }
+}