Update Item doesn't support uploading thumbnail images

[ssylvia]

According to docs, you can add an image file to the thumbnail param that should be uploaded as a thumbnail image.

This does not work:

updateItem({
  authentication: userSession,
  item: {
    ...otherItemDetails,
    thumbnail: MyBlob
  }
}),

However, if I use the standard request, it works:

request('https://www.arcgis.com/sharing/rest/content/users/jsmith/items/2b4c7a08699146f0b270ab609ec4aa91/update',{
  authentication: userSession,
  params: {
    ...otherItemDetails,
    thumbnail: MyBlob
  }
})