Core/Spells: Fixed players being able to mount with all transform auras

Closes #11852

src/server/game/Entities/Unit/Unit.cpp

@@ -13051,9 +13051,35 @@ bool Unit::IsInFeralForm() const
 
 bool Unit::IsInDisallowedMountForm() const
 {
-    ShapeshiftForm form = GetShapeshiftForm();
-    return form != FORM_NONE && form != FORM_BATTLESTANCE && form != FORM_BERSERKERSTANCE && form != FORM_DEFENSIVESTANCE &&
-        form != FORM_SHADOW && form != FORM_STEALTH && form != FORM_UNDEAD;
+    if (ShapeshiftForm form = GetShapeshiftForm())
+    {
+        SpellShapeshiftEntry const* shapeshift = sSpellShapeshiftStore.LookupEntry(form);
+        if (!shapeshift)
+            return true;
+
+        if (!(shapeshift->flags1 & 0x1))
+            return true;
+    }
+
+    if (GetDisplayId() == GetNativeDisplayId())
+        return false;
+
+    CreatureDisplayInfoEntry const* display = sCreatureDisplayInfoStore.LookupEntry(GetDisplayId());
+    if (!display)
+        return true;
+
+    CreatureDisplayInfoExtraEntry const* displayExtra = sCreatureDisplayInfoExtraStore.LookupEntry(display->ExtraId);
+    if (!displayExtra)
+        return true;
+
+    CreatureModelDataEntry const* model = sCreatureModelDataStore.LookupEntry(display->ModelId);
+    ChrRacesEntry const* race = sChrRacesStore.LookupEntry(displayExtra->Race);
+
+    if (model && !(model->Flags & 0x80))
+        if (race && !(race->Flags & 0x4))
+            return true;
+
+    return false;
 }
 
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