Configure
    ...
    .Options( o => { o.EnableIdempotentSagas(); } )
    ...
    .Sagas( s => { s.StoreInMongoDb( mongoDatabase ); } )

{
    "_id" : NUUID("0aa63d69-f8f9-46bd-ab29-f1e46411a166"),
    "Revision" : 1,
    "IdempotencyData" : {},
    ...
}