[{"_id":0,"items":[{"key":"name","value":"y"},{"key":"module","value":"z"}]}]

db.collection.aggregate([{"$set":{"items":{"$map":{"input":"$items","in":{"k":"$$this.key","v":"$$this.value"}}}}},{"$set":{"items":{"$arrayToObject":["$items"]}}},{"$replaceRoot":{"newRoot":{"$mergeObjects":["$items","$$ROOT"]}}},{"$project":{"items":0}}])