Exiles Reach: rider immune to NPC damage while on the giant boar

Some undead still hit the player during the boar ride (mobs that aggro on
sight, not via the trample). Set UNIT_FLAG_IMMUNE_TO_NPC on the player for
the ride's duration so mob attacks can't reach the rider (IsValidAttackTarget
checks target->IsImmuneToNPC); the boar takes the hits and the trample kills
the cadavers.

src/server/scripts/ExilesReach/exiles_reach_darkmaul_plains.cpp

@@ -890,6 +890,18 @@ public:
 
     class spell_riding_giant_boar_305068_AuraScript : public AuraScript
     {
+        void HandleApply(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
+        {
+            Unit* owner = GetUnitOwner();
+            if (!owner)
+                return;
+
+            // Riding the giant boar: the undead chew on the boar, not the rider.
+            // Block NPC attacks on the player (the trample/charge already pull
+            // threat onto the boar, so remaining direct hits shouldn't reach us).
+            owner->SetUnitFlag(UNIT_FLAG_IMMUNE_TO_NPC);
+        }
+
         void HandleRemove(AuraEffect const* /*aurEff*/, AuraEffectHandleModes /*mode*/)
         {
             Unit* owner = GetUnitOwner();
@@ -897,12 +909,14 @@ public:
             if (!owner || !player)
                 return;
 
+            owner->RemoveUnitFlag(UNIT_FLAG_IMMUNE_TO_NPC);
             player->RemoveAura(SPELL_RIDING_GIANT_BOAR2);
             player->CastSpell(player, SPELL_KNOCKBACK_FOR_HACKFIX_GIANT_BOAR_LEAVE, true);
         }
 
         void Register() override
         {
+            OnEffectApply += AuraEffectApplyFn(spell_riding_giant_boar_305068_AuraScript::HandleApply, EFFECT_1, SPELL_AURA_LINKED_SUMMON, AURA_EFFECT_HANDLE_REAL);
             OnEffectRemove += AuraEffectRemoveFn(spell_riding_giant_boar_305068_AuraScript::HandleRemove, EFFECT_1, SPELL_AURA_LINKED_SUMMON, AURA_EFFECT_HANDLE_REAL);
         }
     };