Update ActivityNotFoundActivity to throw exception when executed

src/modules/Elsa.Workflows.Core/Activities/NotFoundActivity.cs

@@ -1,6 +1,7 @@
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using Elsa.Workflows.Core.Attributes;
+using Elsa.Workflows.Core.Exceptions;
 using JetBrains.Annotations;
 
 namespace Elsa.Workflows.Core.Activities;
@@ -38,4 +39,10 @@ public class NotFoundActivity : CodeActivity
     /// The original activity JSON.
     /// </summary>
     public string OriginalActivityJson { get; set; } = default!;
+
+    /// <inheritdoc />
+    protected override void Execute(ActivityExecutionContext context)
+    {
+        throw new ActivityNotFoundException(MissingTypeName, MissingTypeVersion);
+    }
 }

src/modules/Elsa.Workflows.Core/Exceptions/ActivityNotFoundException.cs

@@ -0,0 +1,24 @@
+namespace Elsa.Workflows.Core.Exceptions;
+
+/// <summary>
+/// Thrown when a NotFoundActivity is executed.
+/// </summary>
+public class ActivityNotFoundException : Exception
+{
+    /// <inheritdoc />
+    public ActivityNotFoundException(string missingTypeName, int missingTypeVersion) : base($"Activity type '{missingTypeName}' version '{missingTypeVersion}' could not be found.")
+    {
+        MissingTypeName = missingTypeName;
+        MissingTypeVersion = missingTypeVersion;
+    }
+    
+    /// <summary>
+    /// The type name of the missing activity type.
+    /// </summary>
+    public string MissingTypeName { get; }
+    
+    /// <summary>
+    /// The version of the missing activity type.
+    /// </summary>
+    public int MissingTypeVersion { get; }
+}