Core/Units: add new functionality for units to block or enable combat interactions

Port From (https://github.com/TrinityCore/TrinityCore/commit/2819951dce545438724719836e3a13d3039b8690)

Source/Game/Combat/CombatManager.cs

@@ -57,11 +57,8 @@ namespace Game.Combat
                 return false;
             if (a.HasUnitState(UnitState.InFlight) || b.HasUnitState(UnitState.InFlight))
                 return false;
-            Creature aCreature = a.ToCreature();
+            // ... both units must not be ignoring combat
-            if (aCreature != null && aCreature.IsCombatDisallowed())
+            if (a.IsIgnoringCombat() || b.IsIgnoringCombat())
-                return false;
-            Creature bCreature = b.ToCreature();
-            if (bCreature != null && bCreature.IsCombatDisallowed())
                 return false;
             if (a.IsFriendlyTo(b) || b.IsFriendlyTo(a))
                 return false;

Source/Game/Entities/Creature/Creature.cs

@@ -420,6 +420,8 @@ namespace Game.Entities
                 ApplySpellImmune(0, SpellImmunity.Effect, SpellEffectName.AttackMe, true);
             }
 
+            SetIgnoringCombat(cInfo.FlagsExtra.HasFlag(CreatureFlagsExtra.NoCombat));
+
             LoadTemplateRoot();
             InitializeMovementFlags();
 
@@ -3096,10 +3098,6 @@ namespace Game.Entities
         {
             return GetCreatureTemplate().FlagsExtra.HasAnyFlag(CreatureFlagsExtra.Guard);
         }
-        public bool IsCombatDisallowed()
-        {
-            return GetCreatureTemplate().FlagsExtra.HasFlag(CreatureFlagsExtra.NoCombat);
-        }
         
         public bool CanWalk() { return GetMovementTemplate().IsGroundAllowed(); }
         public override bool CanSwim() { return GetMovementTemplate().IsSwimAllowed() || IsPet();}

Source/Game/Entities/Unit/Unit.Combat.cs

@@ -1491,5 +1491,15 @@ namespace Game.Entities
             UpdateAttackTimeField(att);
             m_attackTimer[(int)att] = (uint)(m_baseAttackSpeed[(int)att] * m_modAttackSpeedPct[(int)att] * remainingTimePct);
         }
+
+        /// <summary>
+        /// returns if the unit is ignoring any combat interaction
+        /// </summary>
+        public bool IsIgnoringCombat() { return _isIgnoringCombat; }
+
+        /// <summary>
+        /// enables/disables combat interaction of this unit.
+        /// </summary>
+        public void SetIgnoringCombat(bool apply) { _isIgnoringCombat = apply; }
     }
 }

Source/Game/Entities/Unit/Unit.Fields.cs

@@ -55,6 +55,7 @@ namespace Game.Entities
         uint[] m_baseAttackSpeed = new uint[(int)WeaponAttackType.Max];
         internal float[] m_modAttackSpeedPct = new float[(int)WeaponAttackType.Max];
         protected uint[] m_attackTimer = new uint[(int)WeaponAttackType.Max];
+        bool _isIgnoringCombat;
 
         // Threat+combat management
         CombatManager m_combatManager;