Delete subscription not triggered when cascade delete
### Summary

If I have a table 'group' and a table 'groupMember' that references the first one by 'groupId' with cascade on delete I would like to trigger the delete subscription on groupMember. Is there an option I need to enable or is this not possible without manually deleting all group members first?

### Additional context

postgraphile: "^4.10.0"
postgraphile-plugin-subscriptions: "1.0.0-alpha.5"

Edit: Sorry, if this is just related to the plugin