db={alert_service_alert:[{"_id":"64e21d83-6f2f-4d70-aeaa-b431e936bb54","alert_name":"novemberAlert","notifications":["8be1e36d-495d-476b-b033-1618d01ee93e","9be1e36d-595d-476b-c033-2618d01ee94f"]}],alert_service_notification:[{"_id":"8be1e36d-495d-476b-b033-1618d01ee93e","name":"Notifiction 1","group_recipients":["a98888a2-e347-4d26-92df-aed8ce4916a9"]},{"_id":"9be1e36d-595d-476b-c033-2618d01ee94f","name":"Notifiction 2","group_recipients":["a98888a2-e347-4d26-92df-aed8ce4917ba"]}],alert_service_group_recipients:[{_id:"a98888a2-e347-4d26-92df-aed8ce4916a9",name:"Group 1"},{_id:"a98888a2-e347-4d26-92df-aed8ce4917ba",name:"Group 2"}]}

db.alert_service_alert.aggregate([{"$addFields":{"uuid":"$_id"}},{"$project":{"_id":0}},{"$lookup":{"from":"alert_service_notification","localField":"notifications","foreignField":"_id","as":"notifications"}},{"$unwind":"$notifications"},{"$lookup":{"from":"alert_service_group_recipients","localField":"notifications.group_recipients","foreignField":"_id","as":"notifications.group_recipients"}},{"$group":{"_id":"$_uuid","original":{"$first":"$$ROOT"},"notification":{"$push":"$notifications"}}},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$original",{"notifications":"$notification"}]}}}])