購入件数／購入額／購入時刻を得る
$ltv_query = \Drupal::database()->select('commerce_payment', 'p')
->condition('p.state', 'completed');
$ltv_query->join('commerce_order', 'o', "o.order_id = p.order_id");
$ltv_query->condition('o.uid', $this->account->id());
$order_count_query = clone $ltv_query;
$order_count_query->condition('p.payment_gateway', 'THIS_GATEWAY', '');
$last_order_query = clone $order_count_query;
$last_order_query
->fields('p', ['amount__number', 'completed'])
->orderBy('p.completed', 'DESC')
->range(0, 1);
$last_order = $last_order_query->execute()->fetchObject();
$last_order_amount = $last_order->amount__number ?? 0;
$last_order_at = $last_order->completed ?? REQUEST_TIME;
$order_count = $order_count_query->countQuery()->execute()->fetchField(); // 購入件数（THIS_GATEWAY以外）
$ltv = $ltv_query->countQuery()->execute()->fetchField(); // 購入件数
$last_order_amount = floor($last_order_amount); // 直近の購入額
$last_order_at = floor((REQUEST_TIME - $last_order_at) / (60*60*24)); // 直近の購入時刻
