Adding badge sticker printer functionality for checkin

[phixom]

As a devday visitor i'd like a faster checkin by scanning a qr-code an get a printed badge sticker as ticket because I don't like waiting in long queues and missing the keynote.

a possible solution could be:

• going to a checkin terminal (could be a smarphone and a badge printer with rapsi)
• scanning qr-code
• printer-client is subscibed via websocket to a mq and waiting for new scanevents for his assigned scanner
• if a new scan event is triggerd, printer-client will print the sticker and send a complete or error response
• after a complete response, qr-code will be tageed as scanned and/or used
• after a error response, rescan is needed
• it should be possible to reactivate tagged qr-codes if there any unexpected errors
• if my sticker is printed my checkin is completed