Sufia 6.x Migration Does not include version creators

[carolyncole]

Descriptive summary

In Sufia 6.x the version export does not include who created the version.

Check out the code written in ScholarSphere to fix this bug: psu-libraries/scholarsphere@54c3c71

Expected behavior

When I export a version the json file should include the person who created the version

Actual behavior

When I export a version no created_by information is exported

Steps to reproduce the behavior

1. run sufia_export
2. check the exported generic_file_*.json to see if the is created by as part of the version information

Related work

Link to related tickets or prior related work here.