refactor!: renamed GameManager to Universe and HierarchyObject to UniverseObject

Engine.Core/Abstract/Assignable/IHasUniverse.cs

@@ -0,0 +1,26 @@
+namespace Syntriax.Engine.Core.Abstract;
+
+/// <summary>
+/// Indicates the object is an <see cref="IAssignable"/> with an assignable <see cref="IUniverse"/> field.
+/// </summary>
+public interface IHasUniverse : IAssignable
+{
+    /// <summary>
+    /// Event triggered when the <see cref="IUniverse"/> value has has been assigned a new value.
+    /// </summary>
+    event UniverseAssignedEventHandler? OnUniverseAssigned;
+
+    /// <inheritdoc cref="IUniverse" />
+    IUniverse Universe { get; }
+
+    /// <summary>
+    /// Assign a value to the <see cref="IUniverse"/> field of this object.
+    /// </summary>
+    /// <param name="universe">New <see cref="IUniverse"/> to assign.</param>
+    /// <returns> 
+    /// <see cref="true"/>, if the value given assigned successfully assigned, <see cref="false"/> if not.
+    /// </returns>
+    bool Assign(IUniverse universe);
+
+    delegate void UniverseAssignedEventHandler(IHasUniverse sender);
+}