ipa-otpd: add support for SSSD OIDC helper
    
    SSSD OIDC helper is used for negotiating with OAUTH2 or OIDC end points
    of external identity providers (IdPs).
    
    ipa-otpd daemon now is capable to take either Issuer URL or individual
    endpoints and call SSSD OIDC helper accordingly.
    
    Communication with SSSD OIDC helper can be debugged with the use of a
    debug variable set in /etc/ipa/default.conf. Man page for
    default.conf(5) has been updated to provide this information.
    
    Fixes: https://pagure.io/freeipa/issue/8805
    
    Signed-off-by: Sumit Bose <sbose@redhat.com>
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Francisco Trivino <ftrivino@redhat.com>
    Reviewed-By: Sumit Bose <sbose@redhat.com>
    Reviewed-By: Francisco Trivino <ftrivino@redhat.com>
    Reviewed-By: Sumit Bose <sbose@redhat.com>