LOG IN - improve error message when backend fails

[ovesemart]

Description of issue:

Clicking the "other device" button at log in when I suppose something is not up and running in backend.

Here we maybe should have a message like:
"Service unavailable at the moment, try again later or contact support if problem persist"
"Tjänsten är tillfälligt otillgänglig, försök igen senare eller kontakta support om problemet kvarstår"

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[ovesemart]

This is a generic issue, that maybe we should handle errors from backend in a generic way.

[ovesemart]

Status of this is unknown