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

app/Domains/Purchase/Resources/PurchaseItemResource.php

@@ -99,10 +99,18 @@ class PurchaseItemResource extends JsonResource
         }
 
         $attributes = $variant->definitions
-            ->map(fn ($definition): array => [
-                'name' => (string) ($definition->itemAttribute?->attribute?->nombre ?? ''),
-                'value' => $definition->value,
-            ])
+            ->groupBy('item_attribute_id')
+            ->map(function ($definitions): array {
+                $itemAttribute = $definitions->first()?->itemAttribute;
+                $values = $definitions->pluck('value')->values();
+
+                return [
+                    'name' => (string) ($itemAttribute?->attribute?->nombre ?? ''),
+                    'value' => $itemAttribute?->allow_multi_select
+                        ? $values->all()
+                        : $values->first(),
+                ];
+            })
             ->filter(fn (array $attribute): bool => $attribute['name'] !== '' || $attribute['value'] !== null)
             ->values();