sdap_get_users_send(): new argument mapped_attrs
    
    mapped_attrs can be a list of sysdb_attrs which are not available on
    the server side but should be store with the cached user entry. This is
    needed e.g. when the input to look up the user in LDAP is not an
    attribute which is stored in LDAP but some data where LDAP attributes
    are extracted from. The current use case is the certificate mapping
    library which can create LDAP search filters based on content of the
    certificate. To allow upcoming cache lookup to use the input directly it
    is stored in the user object in the cache.
    
    Related to https://pagure.io/SSSD/sssd/issue/3050
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>