Stop ringing doorbell for each expired / unknown card

[patrickod]

Currently it appears the bell rings each time someone presents a card that has expired. We should instead provide feedback to the user and leave the doorbell alone, as it's bothersome in the space.

[hzeller]

mmh, but the intention is that the swipe of the card does the next best thing: ring the doorbell to get in. Probably the problem might be that they anyway do that right after that incident, so that we have too many doorbell rings per time-unit ?

Feedback is given to the user by the blue LED.