Core/Creature: Add facilities to the Creature class to allow setting an automated, periodic pulse that puts every player in the zone in combat and on the creature's threat list.

Scripts/BossAI: Set the BossAI parent class to make use of this in its _EnterCombat and _Reset methods. Combat pulses happen every 5 seconds.

src/server/game/AI/ScriptedAI/ScriptedCreature.cpp

@@ -470,6 +470,7 @@ void BossAI::_Reset()
     if (!me->IsAlive())
         return;
 
+    me->SetCombatPulseDelay(0);
     me->ResetLootMode();
     events.Reset();
     summons.DespawnAll();
@@ -500,6 +501,7 @@ void BossAI::_EnterCombat()
         instance->SetBossState(_bossId, IN_PROGRESS);
     }
 
+    me->SetCombatPulseDelay(5);
     me->setActive(true);
     DoZoneInCombat();
     ScheduleTasks();