old_contents: #this file is the only file that is different on each reader device (mobile or fixed reader)
  settings = {
  "readerType": "mobile",
  "readerID": "M2"
  }
  
new_contents: #this file is the only file that is different on each reader device (mobile or fixed reader)
  settings = {
  "readerType": "mobile",
  "readerID": "M1"
  }
  
subject: change reader id