Core/Spells: Implemented SPELL_ATTR9_ONLY_WHEN_ILLEGALLY_MOUNTED

Port From (https://github.com/TrinityCore/TrinityCore/commit/1f3af18e3a17096748a621c9171feb30047287be)

Source/Framework/Constants/Spells/SpellConst.cs

@@ -1968,7 +1968,7 @@ namespace Framework.Constants
     {
         ForceDestLocation = 0x01, // Force Dest Location DESCRIPTION Ignores collision with terrain (unsure if it also ignores terrain height and can go under map)
         ModInvisIncludesParty = 0x02, // Mod Invis Includes Party 1@Attr9 DESCRIPTION Causes invisibility auras to ignore "can always see party member invis" rule
-        RestrictedFlightArea = 0x04, // 2
+        OnlyWhenIllegallyMounted = 0x04, // Only When Illegally Mounted
         Unk3 = 0x08, // 3
         SpecialDelayCalculation = 0x10, // 4
         SummonPlayerTotem = 0x20, // 5

Source/Game/Spells/Spell.cs

@@ -5148,6 +5148,23 @@ namespace Game.Spells
 
                     if (unitCaster.IsInCombat() && !m_spellInfo.CanBeUsedInCombat(unitCaster))
                         return SpellCastResult.AffectingCombat;
+
+                    if (m_spellInfo.HasAttribute(SpellAttr9.OnlyWhenIllegallyMounted))
+                    {
+                        bool hasInvalidMountAura = unitCaster.GetAuraEffectsByType(AuraType.Mounted).Any(mountEffect =>
+                        {
+                            uint mountType = (uint)mountEffect.GetSpellEffectInfo().MiscValueB;
+                            var mountEntry = Global.DB2Mgr.GetMount(mountEffect.GetId());
+                            if (mountEntry != null)
+                                mountType = mountEntry.MountTypeID;
+
+                            var mountCapability = unitCaster.GetMountCapability(mountType);
+                            return mountCapability == null || mountCapability.Id != mountEffect.GetAmount();
+                        });
+
+                        if (!hasInvalidMountAura)
+                            return SpellCastResult.OnlyMounted;
+                    }
                 }
 
                 // Check vehicle flags