One way to send "anything" back to a PB app from any web app using just a URL is to create a custom URL protocol handler that:
- Knows how to trigger events in your PB app
- Listens to whatever URL protocol you decide to use
You can install custom URL protocol handlers on Windows clients via Windows registry.
Alternatively you need your web app to call some REST service when your token is ready - and your PB app to poll that REST service until that token is available. Remember to do everything secured since this is a security token you don't want to expose.
Authority Code is primarily used by web apps because it is quite hard to allow calls from one web app (the login app) to a native win32/win64 app without breaking the security sandbox. I have used custom URL protocol to do that.