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What does this MR do and why?

Adds documentation on a development gotchas where we have guidance on database reversibility, but none on how to rollout token format changes (or other data that will essentially be with clients) in cases of rollbacks

References

Relates to Add development documentation on ensuring rollb... (gitlab-com/gl-infra/production-engineering#27272 - closed)

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How to set up and validate locally

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