These documents are uploaded by a user before confirming a referral.
    They could be images or reports of previous scans for example.
    To upload a file, you must send a multipart/form-data request.
    The request should specify a "file" parameter.
    Like a regular HTML file input named "file".
    Any type of file is accepted.
    Maximum file size is 25MB.
    Several files can be uploaded but they need to be uploaded one by one.