Support checking in with darfichrein QR-codes

[sedrubal]

Feature description

As it is now possible to check in with Luca QR-codes (#530), it was great to also support darfichrein.de QR-codes. Currently this error message is displayed, when you scan a darfichrein.de QR-code with the cwa app:

No suitable QR Code

The QR code cannot be [s]canned by the Corona-Warn-App. Please select a file with a suitable QR code.

This is a follow-up issue to #138.

Problem and motivation

• As you have to enter personal data about yourself to check in with darfichrein, it was more privacy friendly, if you can do that with cwa.
• Users without IT background might not understand, why you sometimes can use the cwa to check in and sometimes you can't.

Is this something you're interested in working on

No

[thomasaugsten]

All 3rd Party Apps needs to contact the RKI to be added on the Allow List.
Technical specification:
https://github.com/corona-warn-app/cwa-documentation/blob/master/event_registration.md#qr-code-compatibility-with-other-contract-tracing-apps-in-germany

[dsarkar]

@sedrubal thanks for the proposal, see #683 (comment)

---

Corona-Warn-App Open Source Team