Today the moderation view (https://archive.softwareheritage.org/admin/deposit/) generates the url of the external-id on the fly
by using <hal-client-url>/<external-id>
This is a problem at present with deposits from the hal-preprod platform, which is not an urgent/big problem.
On the other hand, when the deposit will be open to new clients, this property will be problematic as is.
That's why the url associated to the external-id should be directly taken from the swh-id-context where the origin url is defined.