title: What is the appropriate response and HTTP status code if one file validation fails when uploading multiple files
body: <p>There's an endpoint that performs file upload for upto 5 csv files. The request fails when a user hits the endpoint without sending any file. A user can send just one file or multiple files but not more than five. What appropriate response should the server give for a situation where the user uploads three files where two are csv files and one a txt file?
  Would the server return a 200 or 400 status code and a message stating the files that were successfully uploaded and those not successful. Or would it be more appropriate to return a 400 status code and reject all uploaded files since at least one file wasn't in the right format? </p>
  
  <p>I've considered returning a 200 status code and a message stating the successfully uploaded files while stating the reason other files were not uploaded. I also return 400 status code if none of the uploaded files are in the right format. What do you guys reckon?</p>