Natural keys instead of UUIDs

[dennisvang]

Currently, if we want to use the API to create or change any resource with links to other resources, we first need to determine all the UUIDs for these resources.

This is highly inconvenient.

It would be less of a problem if the API behaved as a hypermedia API, returning available state-transition hyperlinks in the response (as in HATEOAS), but it does not.

Even if it did, it would be much more convenient if we could (also?) refer to a resource by some sort of natural key, instead of a UUID.