Scheduled scans are started even when API credentials are invalid

[WKobes]

When having a valid dashboard account of which the API-credentials are invalidated, it is not possible to manually start a scan (Error message: "Credentials for the internet.nl API are not valid".

However, schedulded scans (biweekly, monthly, etc.) are still started and get stuck in the 'progress.credential_error' state until manually stopped:

I think it would be better if scheduled scans are not started or aborted when the API creds are invalid, especially since the scan cannot be restarted/continued when the credentials are changed.

Also perhaps add a translation for the state 'progress.credential_error'