Core/Spells: Implemented SPELL_ATTR9_CANNOT_KILL_TARGET

Port From (https://github.com/TrinityCore/TrinityCore/commit/b3bdb4efef5d89df023fcccd6975edfd1ebd9903)

Source/Framework/Constants/Spells/SpellConst.cs

@@ -1994,7 +1994,7 @@ namespace Framework.Constants
         DontConsumeChargeIfItemDeleted = 0x2000000, // NYI - some sort of bugfix attribute to prevent double item deletion? // (Programmer Only) Don't consume charge if item deleted
         ItemPassiveOnClient = 0x4000000, // Item Passive On Client
         ForceCorpseTarget = 0x8000000, // Causes the spell to continue executing effects on the target even if one of them kills it
-        Unk28 = 0x10000000, // 28
+        CannotKillTarget = 0x10000000, // Cannot Kill Target
         Unk29 = 0x20000000, // 29
         Unk30 = 0x40000000, // 30
         Unk31 = 0x80000000  // 31

Source/Game/Entities/Unit/Unit.cs

@@ -2782,6 +2782,9 @@ namespace Game.Entities
                 }
             }
 
+            if (spellProto != null && spellProto.HasAttribute(SpellAttr9.CannotKillTarget) && damageTaken >= health)
+                damageTaken = health - 1;
+
             if (attacker != null && attacker != victim)
             {
                 Player killer = attacker.ToPlayer();