* Fix incorrect usage of PAM_IGNORE (YSA-2025-01, CVE-2025-23013).
* Changed return value when nouserok is enabled and the user has no
credentials, PAM_IGNORE is used instead of PAM_SUCCESS.
* Hardened checks of authfile permissions.
* Hardened checks for nouserok.
* Improved debug messages.
* Improved documentation.
OBS-URL: https://build.opensuse.org/package/show/security/pam_u2f?expand=0&rev=26
