Order tax adjustment is treated as shipping tax

[shochdoerfer]

Sylius version affected: 1.12

Description
When trying to add a tax adjustment to an order, the tax adjustment is treated as shipping tax by Sylius. This seems to be a known issue as I found this comment in another issue: #11279 (comment)

Steps to reproduce

class CustomTaxAdjustment implements OrderProcessorInterface
{
    public function __construct(private FactoryInterface $adjustmentFactory)
    {
    }

    public function process(OrderInterface $order): void
    {
        /** @var Adjustment $adjustment */
        $adjustmentVat = $this->adjustmentFactory->createNew();
        $adjustmentVat->setType(AdjustmentInterface::TAX_ADJUSTMENT);
        $adjustmentVat->setAmount(475);
        $adjustmentVat->setLabel('Custom Tax adjustment');
        $adjustmentVat->setOriginCode('tax_adjust');
        $adjustmentVat->setNeutral(false);

        $order->addAdjustment($adjustmentVat);
    }
}

Possible Solution
As outlined in the linked comment, the issue could be solved by either:

• introducing a specific SHIPPING_TAX_ADJUSTMENT
• TAX_ADJUSTMENT on the Shipment level