certmap: add new library libsss_certmap With this library it would be possible to map certificates and users not only by adding the full certificate to the user's LDAP object but by adding e.g. only parts like the issuer and subject name. Additionally the library is also able to flexible select/match certificates based on values in the certificate. Details about mapping and matching rules can be found in the included man page. Related to https://pagure.io/SSSD/sssd/issue/3050 Reviewed-by: Jakub Hrozek <jhrozek@redhat.com> Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>