Recursive delete fix fix (#5819)

* Enable mysql checks as part of PR

* Add debug for CI

* Add delete_nodes method

- Ensure that the "parent" field is set to None before delete
- This means that we do not violate any ForeignKey constraints due to undefined order of operations

.github/workflows/qc_checks.yaml

@@ -274,7 +274,6 @@ jobs:
     runs-on: ubuntu-20.04
 
     needs: [ 'pep_style', 'pre-commit' ]
-    if: github.event_name == 'push'
 
     env:
       # Database backend configuration