`CollectionVersion` content with `certification` values of `needs_review` and `not_certified` exist in the `published` repo as part of the introduction of content promotion #20. These need to be moved respectively to the `staging` and `rejected` repos.

A move means the source repo will get a new `RepositoryVersion` without the content, and the destination repo will get a new `RepositoryVersion` with the content. This is done via model method `Repository.new_version()`

Moving this content inside migrations has a couple challenges: We cannot access model methods. We cannot utilize the tasking system, so no locks would be on the repos, and this would need to be done when no activity was present.

Possible approaches:
1. use a bash script to execute curl posts on all content `move/` endpoints
2. copy appropriate model methods to migrations