Resolve problem with origin data

[naydav]

Full context in documentation

[HLD] Inconsistent saving of Stock Data

Description

We have the following situation in _\Magento\Catalog\Model\Product.php#L2298

/**
 * Check whether stock status changed
 *
 * @return bool
 */
private function isStockStatusChanged()
{
    $stockItem = null;
    $extendedAttributes = $this->getExtensionAttributes();
    if ($extendedAttributes !== null) {
        $stockItem = $extendedAttributes->getStockItem();
    }
    $stockData = $this->getStockData();
    return (
        (is_array($stockData))
        && array_key_exists('is_in_stock', $stockData)
        && (null !== $stockItem)
        && ($stockItem->getIsInStock() != $stockData['is_in_stock'])
    );
}

We need to DELETE or REFACT this code.
So, we need to check the origin of the Stock Status value. We can solve in several ways:

1. [Recommended] Create a mechanism for tracking the origin entity data, based on EntityStateInterface. For this, a separate HLD is required.
2. Use origin data from StockItem like as $stockItem->getOriginData('status')
3. Create a simple model like this:

class ProductOriginStockStatusChecker
{
    public function getValue()
    {
        // resolving from origin data or direct call to db or 
    } 
}

4. Using of private property in Product model for storing stock status data.