Core/Spells: Implemented SPELL_AURA_ALLOW_TALENT_SWAPPING

Port From (https://github.com/TrinityCore/TrinityCore/commit/49b47047b809ce654661df595b14a5f8c1f01c8c)

Source/Game/Spells/Auras/AuraEffect.cs

@@ -2106,6 +2106,22 @@ namespace Game.Spells
             target.ModifySkillBonus(prot, (apply ? points : -points), GetAuraType() == AuraType.ModSkillTalent);
         }
 
+        [AuraEffectHandler(AuraType.AllowTalentSwapping)]
+        void HandleAuraAllowTalentSwapping(AuraApplication aurApp, AuraEffectHandleModes mode, bool apply)
+        {
+            if (!mode.HasAnyFlag(AuraEffectHandleModes.Real))
+                return;
+
+            Player target = aurApp.GetTarget().ToPlayer();
+            if (target == null)
+                return;
+
+            if (apply)
+                target.AddUnitFlag2(UnitFlags2.AllowChangingTalents);
+            else if (!target.HasAuraType(GetAuraType()))
+                target.RemoveUnitFlag2(UnitFlags2.AllowChangingTalents);
+        }
+
         /****************************/
         /***       MOVEMENT       ***/
         /****************************/