Koha::Policy::Patrons::Cardnumber - module to deal with cardnumbers policy
my $is_valid = Koha::Policy::Patrons::Cardnumber->is_valid( $cardnumber, [$patron] );
Returns whether a cardnumber is valid of not for a given Koha::Patron object.
my ($min, $max) = Koha::Policy::Patrons::Cardnumber::get_valid_length();
Returns the minimum and maximum length for patron cardnumbers as determined by the CardnumberLength system preference, the BorrowerMandatoryField system preference, and the width of the database column.