If the onlineMovePrimary feature flag is on, begin applying oplogs that were fetched by the fetcher. Write unit tests if possible to ensure that the integratation works (e.g. oplogs are applied or even simply the metrics are incremented). The ReshardingOplogApplier is somewhat monolithic in that it is an interface in front of multiple classes (e.g. iterator, batcher, applier, application rules). If it's not as simple as standing up this class as-is and having it work (i.e. changes must be made to each of those components individually), then break this ticket into subtasks as necessary.