[{_id:"611e2febb863ce74ac448220",product:{category:5,gender:1,title:"sivdosi",description:"oisbdvoi",price:2394,imageFileName:"http://localhost:3000/images/1628875244435-3564.png"}}]

db.collection.aggregate([{"$addFields":{"product._id":"$_id"}},{$replaceRoot:{newRoot:"$product"}}])