<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=592634) </details> <!--IssueSummary end--> This issue is to add `:offline_transfer` as an import source to [`Import::HasImportSource`](app/models/concerns/import/has_import_source.rb) for logging and observability purposes. Import logging often uses an `importer` or `import_source` attribute to keep record of which import feature generated the log. Offline transfer will need its own import source so that import and export logs are classified properly and aren't mistaken for direct transfer logs.