public function rules(): array 	{ 		return [ 			'lang' => ['nullable', 'string', 'size:2', 'in:hr,en'], 			'items' => ['required', 'array'], 			'items.*.product_id' => ['required', 'uuid', 'exists:products,id'], 			'items.*.variant_id' => ['nullable', 'uuid', 'distinct', 'exists:product_variants,id', 'bail'], 		]; 	}