title: R Shiny REST API communication
body: <p>I have a shiny app that takes a JSON input file, runs it through a classifier and returns a classified JSON object.
  I want the app to be able to communicate with an API. I want the API to post a file to the Shiny App which will do its work and return a classified object.
  Basically I want the Shiny app to sit in the background until a file is posted and then do its work.
  I know that I can use GET from the httr package to get a file from a url. I can put this in the shiny.server file which is fine if I know the file name for the get command</p>
  <p>However the filenames coming from the API will be different. So is there any way that I can make this dynamic according to the Post request that comes from the API.</p>