[keycloak-dev] Async authentication example

I gave it a go and implemented an "async" authentication example. It's rather simple what happens is: * User authenticates with username only * Then a "waiting" page is displayed, which is waiting for some external callback. This could be an app or whatever that verifies the user then sends the callback. In the example a CURL command is printed on sysout for the server which you can run to "simulate" the callback from the app. * Once the callback is received the user is authenticated without filling in password or any other credentials in the main browser https://github.com/stianst/authenticator-example Check it out here: https://youtu.be/C09BpNIf4v8 It's a bit hacky in the way it's implemented: * Using notes for "callback" is a bit strange maybe? * Had to use custom realm resource for callback endpoint. Is this strange? * Probably won't work for cross DC, but in 7.2 Hynek has stuff that does that * No way to push change to browser, so have to pull every 2 seconds. Maybe we could add a simple authentication event feature that uses websockets and a small auth js lib to do the job of notification?