Dash for R API does not currently allow user-defined routes #131

@app.callback(Output('my-link', 'href'), [Input('my-dropdown', 'value')])
def update_link(value):
    return '/dash/urlToDownload?value={}'.format(value)

@app.server.route('/dash/urlToDownload') 
def download_csv():
    value = flask.request.args.get('value')
    # create a dynamic csv or file here using `StringIO` 
    # (instead of writing to the file system)
    strIO = StringIO.StringIO()
    strIO.write('You have selected {}'.format(value)) 
    strIO.seek(0)    
    return send_file(strIO,
                     mimetype='text/csv',
                     attachment_filename='downloadFile.csv',
                     as_attachment=True)

plugin <- list(
    on_attach = function(server) {
     router <- server$plugins$request_routr
     route <- Route$new()
     route$add_handler('all', '*', function(request, response, arg_list, ...) {
       message('Hello')
       TRUE
    })
    router$add_route(route, 1)
    },
  name = 'Hello_plugin',
  require = 'request_routr'
)