Bug 32330: Add indexes to table background_jobs

Bug 32330: Add indexes to table background_jobs

Table background_jobs should have indexes to optimize queries.

Query on borrowernumber :
mainpage.pl:    my $already_ran_jobs = Koha::BackgroundJobs->search(
mainpage.pl-        { borrowernumber => $logged_in_user->borrowernumber } )->count ? 1 : 0;

Query on status and queue :
misc/background_jobs_worker.pl:        my $jobs = Koha::BackgroundJobs->search({ status => 'new', queue => \@queues });

Test plan :
Run updatedatabase and play with background jobs

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>