Core/Spells: Implemented SPELL_ATTR9_MOD_INVIS_INCLUDES_PARTY

Port From (https://github.com/TrinityCore/TrinityCore/commit/050bde08af9015e9adeaa3bf2b35f08dc210680e)

Source/Framework/Constants/Spells/SpellConst.cs

@@ -1967,7 +1967,7 @@ namespace Framework.Constants
     public enum SpellAttr9 : uint
     {
         ForceDestLocation = 0x01, // Force Dest Location DESCRIPTION Ignores collision with terrain (unsure if it also ignores terrain height and can go under map)
-        Unk1 = 0x02, // 1
+        ModInvisIncludesParty = 0x02, // Mod Invis Includes Party 1@Attr9 DESCRIPTION Causes invisibility auras to ignore "can always see party member invis" rule
         RestrictedFlightArea = 0x04, // 2
         Unk3 = 0x08, // 3
         SpecialDelayCalculation = 0x10, // 4

Source/Game/Entities/Player/Player.cs

@@ -3945,7 +3945,7 @@ namespace Game.Entities
 
             Player seerPlayer = seer.ToPlayer();
             if (seerPlayer != null)
-                if (IsGroupVisibleFor(seerPlayer))
+                if (IsGroupVisibleFor(seerPlayer) && !GetAuraEffectsByType(AuraType.ModInvisibility).All(invis => invis.GetSpellInfo().HasAttribute(SpellAttr9.ModInvisIncludesParty)))
                     return true;
 
             return false;