Problem/Motivation
We need a standardized and complete way to copy config between two config storages.
Many tools such as drush and drupal console and also a couple of modules do this all in their own way now and some do it in a incomplete fashion that may lead to strange behaviour in edge cases.
Proposed resolution
Add a utility class to copy config between storages which also takes care of collections.
Remaining tasks
port code from #2991683: Add configuration transformer API
review
commit
User interface changes
none
API changes
todo