curl --request PATCH \
  --url https://realtime-api.voiceflow.com/v1/stable/document/{documentID} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "metadata": [
    {
      "key": "<string>",
      "values": [
        "<string>"
      ]
    }
  ]
}
'

{
  "message": "<string>"
}