Noticed some acceptance tests failing due to a bug in the Managed Database flattenReplicas function, always trying to flatten the FerretDB credentials object even if it didn't exist. Removed it from the main map/interface block and setting that separately for the correct engine type only seems to do the trick.
Checklist:
[x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
[x] Have you linted your code locally prior to submission?
[x] Have you successfully ran tests with your changes locally?
Description
Noticed some acceptance tests failing due to a bug in the Managed Database flattenReplicas function, always trying to flatten the FerretDB credentials object even if it didn't exist. Removed it from the main map/interface block and setting that separately for the correct engine type only seems to do the trick.
Checklist: