fix(Scripts/ZulGurub): Gah'zranka's Slam should reset threat. (#11910)

data/sql/updates/pending_db_world/rev_1653826897656877600.sql

@@ -0,0 +1,4 @@
+--
+DELETE FROM `spell_script_names` WHERE `spell_id`=24326;
+INSERT INTO `spell_script_names` VALUES
+(24326,'spell_gahzranka_slam');

src/server/scripts/EasternKingdoms/ZulGurub/boss_gahzranka.cpp

@@ -24,6 +24,7 @@ EndScriptData */
 
 #include "ScriptMgr.h"
 #include "ScriptedCreature.h"
+#include "SpellScript.h"
 #include "zulgurub.h"
 
 enum Spells
@@ -110,7 +111,44 @@ public:
     }
 };
 
+class spell_gahzranka_slam : public SpellScript
+{
+    PrepareSpellScript(spell_gahzranka_slam);
+
+    void FilterTargets(std::list<WorldObject*>& targets)
+    {
+        if (Unit* caster = GetCaster())
+        {
+            _wipeThreat = targets.size() < caster->GetThreatMgr().getThreatList().size();
+        }
+    }
+
+    void HandleWipeThreat(SpellEffIndex /*effIndex*/)
+    {
+        if (_wipeThreat)
+        {
+            if (Unit* caster = GetCaster())
+            {
+                if (Unit* target = GetHitUnit())
+                {
+                    caster->GetThreatMgr().modifyThreatPercent(target, -100);
+                }
+            }
+        }
+    }
+
+    void Register() override
+    {
+        OnObjectAreaTargetSelect += SpellObjectAreaTargetSelectFn(spell_gahzranka_slam::FilterTargets, EFFECT_1, TARGET_UNIT_SRC_AREA_ENEMY);
+        OnEffectHitTarget += SpellEffectFn(spell_gahzranka_slam::HandleWipeThreat, EFFECT_1, SPELL_EFFECT_KNOCK_BACK);
+    }
+
+private:
+    bool _wipeThreat = false;
+};
+
 void AddSC_boss_gahzranka()
 {
     new boss_gahzranka();
+    RegisterSpellScript(spell_gahzranka_slam);
 }