/**
 * Allocates an optime for a new entry in the oplog, and updates the replication coordinator to
 * reflect that new optime.  Returns the new optime and the correct value of the "h" field for
 * the new oplog entry.
 *
 * NOTE: From the time this function returns to the time that the new oplog entry is written
 * to the storage system, all errors must be considered fatal.  This is because the this
 * function registers the new optime with the storage system and the replication coordinator,
 * and provides no facility to revert those registrations on rollback.
 */
void getNextOpTime(OperationContext* opCtx,
                   Collection* oplog,
                   ReplicationCoordinator* replCoord,
                   ReplicationCoordinator::Mode replicationMode,
                   unsigned count,
                   OplogSlot* slotsOut) {