Merge incoming data onto already existing data in aggregation pipeline

Working with Data
,
3

Here is a rough example of an aggregation I did.

[{$lookup: {
 from: 'skins',
 localField: 'items._id',
 foreignField: '_id',
 as: 'merged'
}}, {$unwind: {
 path: '$items'
}}, {$unwind: {
 path: '$merged'
}}, {$project: {
 test: {
  $mergeObjects: [
   '$merged',
   '$items'
  ]
 }
}}]

This merges the root level items in the object, but not the content in the “wears” array.