public function rules(): array 	{ 		return [ 			'items' => ['required', 'array'], 			// 'items.*.product_id' => ['required', 'uuid', 'exists:products,id'], 			'items.*.variant_id' => ['nullable', 'uuid', 'distinct', 'exists:product_variants,id', 'bail'], 			'items.*.quantity' => ['required', 'integer', 'min:0'], 		]; 	}