[Feature] Add special ability to block /open (#2506)

This adds the IMMUNE_OPEN (53) special ability to prevent /open on
LDON_TREASURE classes.

zone/client.cpp

@@ -5028,6 +5028,12 @@ void Client::HandleLDoNOpen(NPC *target)
 			return;
 		}
 
+		if (target->GetSpecialAbility(IMMUNE_OPEN))
+		{
+			LogDebug("[{}] tried to open [{}] but it was immune", GetName(), target->GetName());
+			return;
+		}
+
 		if(DistanceSquaredNoZ(m_Position, target->GetPosition()) > RuleI(Adventure, LDoNTrapDistanceUse))
 		{
 			LogDebug("[{}] tried to open [{}] but [{}] was out of range",

zone/common.h

@@ -210,7 +210,8 @@ enum {
 	IMMUNE_AGGRO_NPC = 50,
 	MODIFY_AVOID_DAMAGE = 51,                    //Modify by percent the NPCs chance to riposte, block, parry or dodge individually, or for all skills
 	IMMUNE_FADING_MEMORIES = 52,
-	MAX_SPECIAL_ATTACK = 53
+	IMMUNE_OPEN = 53,
+	MAX_SPECIAL_ATTACK
 };
 
 typedef enum {	//fear states

zone/lua_mob.cpp

@@ -2952,7 +2952,8 @@ luabind::scope lua_register_special_abilities() {
 				luabind::value("immune_damage_npc", static_cast<int>(IMMUNE_DAMAGE_NPC)),
 				luabind::value("immune_aggro_client", static_cast<int>(IMMUNE_AGGRO_CLIENT)),
 				luabind::value("immune_aggro_npc", static_cast<int>(IMMUNE_AGGRO_NPC)),
-				luabind::value("modify_avoid_damage", static_cast<int>(MODIFY_AVOID_DAMAGE))
+				luabind::value("modify_avoid_damage", static_cast<int>(MODIFY_AVOID_DAMAGE)),
+				luabind::value("immune_open", static_cast<int>(IMMUNE_OPEN))
 		];
 }