refactor: Actions to Delegates

Engine.Core/Abstract/Assignable/IAssignable.cs

@@ -1,5 +1,3 @@
-using System;
-
 namespace Syntriax.Engine.Core.Abstract;
 
 /// <summary>
@@ -10,7 +8,7 @@ public interface IAssignable
     /// <summary>
     /// Event triggered when the <see cref="IAssignable"/>'s fields are unassigned and completely ready to recycle.
     /// </summary> 
-    Action<IAssignable>? OnUnassigned { get; set; }
+    event OnUnassignedDelegate? OnUnassigned;
 
     /// <summary>
     /// Unassign <see cref="IAssignable"/>'s all fields and make it ready to recycle.
@@ -19,4 +17,6 @@ public interface IAssignable
     /// <see cref="true"/>, if the fields are unsigned successfully, <see cref="false"/> if not.
     /// </returns>
     bool Unassign();
+
+    delegate void OnUnassignedDelegate(IAssignable sender);
 }