We want to output the total number of open transactions in the "transactions" serverStatus section by utilizing the existing metrics tracked in ServerTransactionsMetrics::currentOpen. We need to add a currentOpen field to the transactions_stats.idl class, so that we can serialize the counter to the serverStatus output object in the TransactionsSSS::generateSection method. The TransactionsSSS::generateSection method returns a BSON object that goes into the transactions section of the serverStatus output.