Добавил домен

backend/UniVerse.Domain/Exceptions/ConflictException.cs

@@ -0,0 +1,8 @@
+namespace UniVerse.Domain.Exceptions;
+
+public class ConflictException : Exception
+{
+    public ConflictException(string message) : base(message)
+    {
+    }
+}

backend/UniVerse.Domain/Exceptions/ForbiddenException.cs

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+namespace UniVerse.Domain.Exceptions;
+
+public class ForbiddenException : Exception
+{
+    public ForbiddenException(string message = "You do not have permission to perform this action.")
+        : base(message)
+    {
+    }
+}

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)
+    {
+    }
+}