by adding the existing credential id to the 'excludeCredentials' list
this prevents the browser from registering a token twice, which
lets authentication fail on some browser/token combinations
(e.g. onlykey/solokey+chromium)
while is seems this is currently a bug in chromium, in a future spec
update the underlying behaviour should be better defined, making this
an authenticator bug
also explicitly catch registering errors and show appropriate error messages
0: https://bugs.chromium.org/p/chromium/issues/detail?id=1087642
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>