We need to drop the config.placementHistory collection on the config server while modifying shard metadata, insert a single document and run the resetPlacementHistory command. The document should have the following shape:

{
_id: <OID>, // auto-generated 
nss: string, // references db or collection
timestamp: Timestamp, // must strictly relate to the cluster time of the destination cluster
shards: array<ShardId> // may be empty
uuid: UUID // may be missing
}

We should unit test this, and I believe we should get test coverage in jstests with SERVER -90317.