Allow users to configure which referenced entities to export

Here is a patch that adds this feature.

Thanks for the patch.

I don't understand why the current feature Skip entity types to be exported indirectly by reference or in site export isn't sufficient.

We have a similar use case. We export Product Variations with references but skip references to other Product Variations. And this is already working.

I know that it might be confusing that the existing skip_entity_types has a dual use. It skips these types during a site export. And it skips these types if referenced.

So if you explicitly export "node" with references and skip the type "node", it should only skip referenced nodes.

I just noticed that the intended behaviour only works with the search_api backend, but not with the standard batches. This is a bug.

Using the patch in #6, the behaviour should be consistent in all export variations as described in #4.

Can you test it?

I improved my patch a bit and committed it.
If you still discover problems, report them.

Oh cool... thank-you very much for your help!!! I will grab the latest and continue testing. Cheers.

Tested and works as expected now! Thank-you again.

Thanks for the feedback!