Bug 33568: Course reserves

Bug 33568: Course reserves

FIXME We need tests here

FIXME/TODO - Isn't it possible to replace all this mess with the
following Koha::Item method and a new DBIC rs?
sub courses {
    my ($self) = @_;
    return Koha::Courses->search(
        { 'ci.itemnumber' => $self->itemnumber },
        { join            => { course_reserves => 'ci' } }
    );
}

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Laurence Rault <laurence.rault@biblibre.com>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: Tomás Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>