[{"ordernumber":21001,"ordername":"testorder1","status":"Ordered","modifiedat":ISODate("2021-06-30T17:02:17.165Z")},{"ordernumber":21001,"ordername":"testorder1","status":"Order Received","modifiedat":ISODate("2021-07-01T03:57:47.533Z")},{"ordernumber":21001,"ordername":"testorder1","status":"Delivered","modifiedat":ISODate("2021-08-17T23:53:24.878Z")},{"ordernumber":21002,"ordername":"testorder2","status":"Ordered","modifiedat":ISODate("2021-07-17T23:53:24.878Z")},{"ordernumber":21002,"ordername":"testorder2","status":"Order Received","modifiedat":ISODate("2021-07-19T04:07:47.686Z")},{"ordernumber":21002,"ordername":"testorder2","status":"Order Cancelled","modifiedat":ISODate("2021-07-20T15:42:23.123Z")}]

db.collection.aggregate([{"$addFields":{"orderlog":"$$ROOT"}},{$project:{"orderlog":{"_id":0,"ordernumber":0,"ordername":0}}},{$group:{_id:{ordernumber:"$ordernumber",ordername:"$ordername"},orderlogs:{$push:"$orderlog"}}},{$project:{_id:0,ordernumber:"$_id.ordernumber",ordername:"$_id.ordername",orderlogs:"$orderlogs"}}])