Draft: Update group two factor requirement in service

What does this MR do and why?

• Was previously in a callback, changed from an after_save to an after_commit here: !95424 (merged)
• Was originally added as a callback due to MR feedback: "It would be better to run this in a callback, so it's in the same transaction as the save" (gitlab-foss!8763 (comment 22436612))
• Given that this is now in an after_commit, it is not part of the same transaction anyway. Plus, it happens async so the single transaction part is not relevant.
• This is a refactor not a behavior change. The hope is that moving code out of callbacks and into service objects makes it easier to read and understand.
• #371552 (closed)

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