More a question than a request of change (because I'm new to this code base), but where in this change we verify that *an* external_id is actually present and not simply missing? It is totally right to make external_id optional *as a metadata field*, but it should not be missing entirely---the client should be providing an UUID if it's not being provided by other means. In that case, though, the code that generate the complete URL should check that, one way or another, *an* external_id is present, as a safety net.

More a question than a request of change (because I'm new to this code base), but where in this change we verify that *an* external_id is actually present and not simply missing?

So far, we don't check.

In the current workflow with hal, it is provided (and i don't expect that to change because the slug is still mandatory on the api).
Also, with the deposit client cli, we do generate it if not provided (and then associating it to the deposit).
So i expect this to be always present...

I can add the check but i'm not sure what to do if the cases arise, raising?