Magento 2 Custom module upgrade: PHP Serialized to JSON
After the latest Database data format changes in Magento 2.2.x version, there is a need to convert existing PHP serialized data to JSON format. The new release provides upgrade scripts that convert Magento serialized data. But how to deal with custom extensions, which also use automatic serialization mechanism provided by Magento framework? Thankfully, Magento took care of that too.