Geo: Verify attachments on secondaries
Description
It is possible, if unlikely, for synced attachments on secondaries to not match the files on the primary due to bugs causing files to change/move/be deleted on the primary or the secondary.
We had an actual case of checksum mismatch on the primary https://gitlab.com/gitlab-org/gitlab-ee/issues/5524 due to infrastructure issues at the time.
We have an actual case of checksum mismatch on the secondary here: https://gitlab.com/gitlab-org/gitlab-ee/issues/5745
Proposal
- Periodically recalculate stored checksums on the primary, and update if mismatch
- Periodically recalculate stored checksums on the secondary, and mark for resync if mismatch