=head3 custom_cover_image_url

my $image_url = $biblio->custom_cover_image_url

Return the specific url of the cover image for this bibliographic record.

It is built regaring the value of the system preference CustomCoverImagesURL

=cut

sub custom_cover_image_url {

    my ( $self ) = @_;

    my $url = C4::Context->preference('CustomCoverImagesURL');

    if ( $url =~ m|%isbn%| ) {

        my $isbn = $self->biblioitem->isbn;

        $url =~ s|%isbn%|$isbn|g;

    }

    if ( $url =~ m|%issn%| ) {

        my $issn = $self->biblioitem->issn;

        $url =~ s|%issn%|$issn|g;

    }

    return $url;

}