refactor(variant): enhance selection values handling for multi-select attributes

app/Domains/Catalog/Models/Variant.php

@@ -109,10 +109,23 @@ class Variant extends Model
     public function selectionValues(): Collection
     {
         $values = $this->definitions
-            ->mapWithKeys(fn ($definition) => [
-                $definition->itemAttribute?->attribute?->codigo => $definition->value,
-            ])
-            ->filter(fn ($value, $key): bool => $key !== null);
+            ->groupBy('item_attribute_id')
+            ->mapWithKeys(function (Collection $definitions): array {
+                $itemAttribute = $definitions->first()?->itemAttribute;
+                $attributeCode = $itemAttribute?->attribute?->codigo;
+
+                if ($attributeCode === null) {
+                    return [];
+                }
+
+                $definitionValues = $definitions->pluck('value')->values();
+
+                return [
+                    $attributeCode => $itemAttribute->allow_multi_select
+                        ? $definitionValues->all()
+                        : $definitionValues->first(),
+                ];
+            });
 
         $eventDateIds = $this->selectedEventDates()
             ->pluck('id')