In the current dual state where tables and columns can be added/altered/removed either via setup scripts (those located in the Setup folder) or via the new etc/db_schema.xml files, Magento can not know by itself which tables/columns can be safely altered using only the db_schema.xml files. Hence, the db_schema_whitelist.json holds a list of all the DB tables,...
I just came across this problem.
It was caused by the long list of pending cron jobs in table cron_schedule. I backed up the database then truncated table 'cron_schedule' with command
TRUNCATE TABLE cron_schedule;
After this I reindex data and manually ran cron jobs with command bin/magenot cron:run
After this I was able to create/save products as normal. ...
You need to copy manually in plugin on \Magento\Quote\Model\Quote\Address\ToOrderAddress::convert.
For examples, see Magento plugins (EE only unfortunately):
Reason for this is ...
\Magento\Framework\Data\OptionSourceInterface is used when creating source model for system.xml configurations. And can be used with any other custom requirement.
AbstractSource is specifically for EAV attributes.
Replace use \Magento\Framework\Model\AbstractModel with use Magento\Framework\Model\AbstractModel . I am suggesting to remove slash.
Edited: - You can see in this picture the class file is present and its not 404.
There's a Magento patch SUPEE-5984, which addresses these kinds of Enterprise Refresh Index problems.
You can find the patch at https://github.com/brentwpeterson/magento-patches/blob/master/EE1.14/PATCH_SUPEE-5984_EE_18.104.22.168_v1.sh