Add possibility to generate URLs that set card code after registration

[ondryaso]

In (near:tm:) future, there will be a thermal printer in the club. We could also use it in the registration workflow.

Currently, a person comes to the bar, taps their card which generates a registration code in KIS that the barman writes on a piece of paper with a QR code to Kachna Online's homepage and instructions.

With the printer available, the KIS frontend could print out a piece of paper with the QR code that would contain the generated registration code in its URL. When this URL is opened, the code would be saved to a local storage and when the user completes their registration, the app would automatically send a KIS card pairing request with the code saved in the local storage.

Changes needed in KO:

• When the homepage is opened with ?cardCode=XXXXX in the URL's query:
  • Either save that field to sessionStorage; or
  • send it to KIS immediately if the user is already logged in (this must be done only after we know for sure that the current KIS access token is valid).
• When the user confirms their registration (and thus logs in), send that to the KIS /users/me/rfid endpoint, just like if they typed it into the Kód karty field in the profile page. Clear the sessionStorage field.
• If the request fails, show an error message prompting the user to try it again manually or to ask for a new code at the bar.