@app.route('/file', methods=["POST"])
def upload_file():
    if "user_file" not in request.files:
        return "No user_file key in request.files"
    file    = request.files["user_file"]
    if file.filename == "":
        return "Please select a file"
    # get url from s3
    output = upload_to_aws_s3(file, S3_BUCKET)
    return str(output)