auctions-1.0.x-dev/modules/auctions_commerce/auctions_commerce.install

<?php
use Drupal\commerce_order\Entity\OrderItemType;

/**
 * Implements hook_install().
 */
function auctions_commerce_install() {
  // Create the order item type for 'auction_item' if it doesn't already exist.
  if (!OrderItemType::load('auction_item')) {
    $order_item_type = OrderItemType::create([
      'id' => 'auction_item',
      'label' => 'Auction Item',
      'purchasable_entity_type' => 'commerce_product_variation',
      'order_type' => 'default',
      'entity_type' => 'commerce_order_item',
    ]);
    $order_item_type->save();

    // Optionally set default quantity, title generation, or price handling.
  }
}


/**
 * Implements hook_uninstall().
 */
function auctions_commerce_uninstall() {
  // Delete the 'auction_item' order item type if it exists.
  if ($order_item_type = OrderItemType::load('auction_item')) {
    $order_item_type->delete();
  }
}