We need to add a file migrator to mark all .cfg files and automatically rename and convert them to .config version.
Here is the specification of the .config format that we should be following: https://sling.apache.org/documentation/bundles/configuration-installer-factory.html#configuration-files-config-1
One big issue will be comments. In the .config file format only one comment is allowed and that is the first line. No multiline or comments in the middle of the file (or end of a line).
If there are comments in the original file, we could extract those comments to another file <configFileName>.txt and in the new .config file add a singleline comment at the top of the file that mentions the file that the <configFileName>.txt has been created