Print server response in to nextcloud log if error occurs

[Tarry91]

It would be helpful to print some information to the nextcloud log if verifiying an OTP fails. I think especially about the "status" string as described here -->https://developers.yubico.com/OTP/Specifications/OTP_validation_protocol.html This would be helpful for administrators debugging login issues of users.

If the Try an OTP feature on the admin page is used the error codes could be displayed directly additionaly to printing it to the log.

Copying from the yubicloud API documentation:

name	meaning
OK	The OTP is valid.
BAD_OTP	The OTP is invalid format.
REPLAYED_OTP	The OTP has already been seen by the service.
BAD_SIGNATURE	The HMAC signature verification failed.
MISSING_PARAMETER	The request lacks a parameter.
NO_SUCH_CLIENT	The request id does not exist.
OPERATION_NOT_ALLOWED	The request id is not allowed to verify OTPs.
BACKEND_ERROR	Unexpected error in our server. Please contact us if you see this error.
NOT_ENOUGH_ANSWERS	Server could not get requested number of syncs during before timeout
REPLAYED_REQUEST	Server has seen the OTP/Nonce combination before

[jaark]

Basic server response is now added when testing Yubikey server configuration and when adding a key to your account. No response information is (deliberately) given during normal authentication as doing so would risk providing sensitive information to an attacker.