Add published_by to CI Catalog Resource Version

What does this MR do and why?

This MR adds published_by to CI Catalog Resource Version because publishing will be a separate endpoint and we want to validate / store the publisher.

published_by is the user who publishes the CI Catalog Resource Version. It must be equal to the release author because creating a release and publishing a version must be done in a single session via release-cli.

A user can be deleted but it does not mean that we should delete versions. So, our foreign key strategy here is "nullify". This is also one of the reasons why we require this validation only on: :create.

For old data, we'll implement a background migration to copy release.author to version.published_by.

Related to #442783 (closed)

Implementation table

Step	Status
Extract CI catalog component builder into a ser... (!159703 - merged)	✅
Add published_by to CI Catalog Resource Version (!162843 - merged)	⏳
Migration from release.author to version.published_by	TODO
API Endpoint for CI Catalog Publish	TODO

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