WIP: rake gitlab:artifacts:migrate tries to migrate migrated artifacts again

What does this MR do?

rake gitlab:artifacts:migrate has the following code

# lib/tasks/gitlab/artifacts.rake

task migrate: :environment do
  logger = Logger.new(STDOUT)
  logger.info('Starting transfer of artifacts')

  Ci::Build.joins(:project)
    .with_artifacts_stored_locally
    .find_each(batch_size: 10) do |build|
    begin
      build.artifacts_file.migrate!(ObjectStoreUploader::REMOTE_STORE)
      build.artifacts_metadata.migrate!(ObjectStoreUploader::REMOTE_STORE)

with_artifacts_stored_locally refers ci_builds.artifacts_file_store

# app/models/ci/build.rb

class Build < CommitStatus
  scope :with_artifacts_stored_locally, ->() { with_artifacts.where(artifacts_file_store: [nil, LegacyArtifactUploader::LOCAL_STORE]) }

However, if build.artifacts_file and build.artifacts_metadata are ci_job_artifacts, they don't update ci_builds.artifacts_file_store. Instead, they update ci_job_artifacts.file_store.

So I assume rake gitlab:artifacts:migrate tries to migrate migrated artifacts again and again, if it's ci_job_artifacts.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan

What are the relevant issue numbers?

/cc @ayufan @zj @grzesiek