Init

Prefab/Domain/Exceptions/ConcurrencyException.cs

@@ -0,0 +1,9 @@
+namespace Prefab.Domain.Exceptions;
+
+/// <summary>
+/// Thrown when a concurrency conflict is detected.
+/// </summary>
+public class ConcurrencyException : DomainException
+{
+    public ConcurrencyException() : base("The record you attempted to modify was changed by another process.") { }
+}

Prefab/Domain/Exceptions/DomainException.cs

@@ -0,0 +1,6 @@
+namespace Prefab.Domain.Exceptions;
+
+/// <summary>
+/// Root of all domain‐rule violations.
+/// </summary>
+public class DomainException(string message) : Exception(message);