Move import rake task classes into a service
<!--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=341960) </details> <!--IssueSummary end--> The following discussion from !71402 should be addressed: - [ ] @dstull started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/71402#note_690454033): (+1 comment) > A lot of code in here that is hard to test due to placement in a rake task and reduces the ability to DRY up the code with other areas... > > Should we spawn a follow-up to discuss moving the classes defined in here to a more testable area like services?
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