feat: Added IAssignable.Unassign()

Engine.Core/Abstract/Assignable/IAssignable.cs

@@ -1,6 +1,22 @@
+using System;
+
 namespace Syntriax.Engine.Core.Abstract;
 
 /// <summary>
 /// Indicates the class implementing it has Assignable fields that are necessary for the engine to work properly.
 /// </summary>
-public interface IAssignable { }
+public interface IAssignable
+{
+    /// <summary>
+    /// Callback triggered when the <see cref="IAssignable"/>'s fields are unassigned and completely ready to recycle.
+    /// </summary> 
+    Action<IAssignable>? OnUnassigned { get; set; }
+
+    /// <summary>
+    /// Unassign <see cref="IAssignable"/>'s all fields and make it ready to recycle.
+    /// </summary>
+    /// <returns> 
+    /// <see cref="true"/>, if the fields are unsigned successfully, <see cref="false"/> if not.
+    /// </returns>
+    bool Unassign();
+}