[OMP] Deleting a series deletes related publications

[jonasraoni]

Describe the bug
If you remove a series that have a submission assigned, the submission will lose its publication and disappear from the list of submissions.

⚠ It's definitely needed to check if other applications are affected, and probably review our foreign keys (we can add restrict rules or if to go cascade all the way down, then software locks must be placed at strategic points).

To Reproduce

1. Create a series
2. Assign a submission to it
3. Remove the series

What application are you using?
OMP 3.4.0rc1

[touhidurabir]

I believe the right behaviour for this is not to allow a series to get deleted if it has any submission associated with it like what we have for OJS(association of submission with section) .

[jonasraoni]

Yep, this is the behavior that I saw in another similar form, so I think it's ok to follow the pattern.

Something better would be to offer a new field, to allow the user select a "redirection" (e.g. move all submissions to section X before deleting this one).

[touhidurabir]

@asmecher PR to review

omp --> pkp/omp#1367

[asmecher]

@touhidurabir, looks good, but can you also change the ON DELETE CASCADE condition on the foreign key to a set null? (See classes/migration/install/OMPMigration.php and classes/migration/upgrade/v3_4_0/I6093_AddForeignKeys.php where they set up the publications_series_id foreign key constraint.)

[touhidurabir]

@asmecher I have rebased the PR, should be good to merge .

[asmecher]

Merged, thanks!