Allow Backorder for Admins only Magento 2

Question

Does anyone know how we can setup to allow backorders to happen only for orders placed in the backend admin?

So customers on the frontend store would not be able to place an order for an out of stock item.

Our sales reps need to be able to place orders for products that are out of stock, but not our frontend customers.

Is there an extension that would do this or any help would be greatly appreciated.

Answer 1

My solution: change function get Config backorders

1- Create di.xml file in your module Vendor/Module/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">

<type name="Magento\CatalogInventory\Model\Configuration">
    <plugin name="custom_get_backorders" type="Vendor\Module\Plugin\CustomBackorders" sortOrder="1" disabled="false"/>
</type>

2- Create CustomBackorders.php file

Vendor/Module/Plugin/CustomBackorders.php

<?php

namespace Vendor\Module\Plugin;

use Magento\Backend\Model\Auth\Session as BackendSession;

class CustomBackorders
{

    /**
     * @var BackendSession
     */
    protected $_backendSession;

    public function __construct(
        BackendSession $backendSession
    )
    {
        $this->_backendSession = $backendSession;
    }

    public function afterGetBackorders(\Magento\CatalogInventory\Model\Configuration $subject, $result)
    {
        if ($this->_backendSession->isLoggedIn()) {
            $result = (int)1;
        }

        return $result;
    }
}