ResourceDefinition children and external-links are duplicated after every save

[dennisvang]

How to reproduce:

1. Run compose/fdp/ephemeral/v2/dev/fdp to set up postgres and fdp-client
2. Run the current develop branch (e746e9a), with development profile,, from source
3. Using a browser, visit the fdp-client at http://localhost:80
4. Log in as the default admin@example.com
5. Visit the "Edit Catalog" page (e.g. http://localhost/resource-definitions/a0949e72-4466-4d53-8900-9436d1049a4b)
6. Observe that there are n child resources called Dataset (n=1, by default)
7. Click "Save"
8. Visit the "Edit Catalog" page again
9. Observe that there are now 2*n child resources called Dataset
10. repeat steps 7. to 9. until convinced.

This leads to the following:

UPDATE:

The same happens for external links. This can be reproduced by repeating the steps above with the default Distribution resource.

[dennisvang]

One observation is that deleteDependents does not actually delete the children, despite L249

FAIRDataPoint/src/main/java/org/fairdatapoint/service/resource/ResourceDefinitionService.java

Lines 248 to 249 in f65cd35

	protected void deleteDependents(ResourceDefinition resourceDefinition) {
	resourceDefinition.getChildren().forEach(this::deleteChild);

The delete call from deleteChild L260 does cause the entity state to be DELETED in the persistence context, but no SQL delete statement is created when flush is called in L252

FAIRDataPoint/src/main/java/org/fairdatapoint/service/resource/ResourceDefinitionService.java

Lines 258 to 260 in f65cd35

	protected void deleteChild(ResourceDefinitionChild child) {
	childMetadataRepository.deleteAll(child.getMetadata());
	childRepository.delete(child);

Here's part of the logs showing that the deletion is being "un-scheduled":

[TRACE] 2026-01-23 14:00:11.660 [main] DefaultPersistEventListener -
un-scheduling entity deletion [[org.fairdatapoint.entity.resource.ResourceDefinitionChild#e9f0f5d3-2a93-4aa3-9dd0-acb1d76f54fc]]

This probably has to do with improper management of the bi-directional relation, e.g. deleting the relation from the link entity (ResourceDefinitionChild) without deleting the item from the parent ResourceDefinition's children.