Handle cases where referenced contextual entities are not described elsewhere in the file

[elichad]

It's not mandatory to describe referenced contextual entities - see https://www.researchobject.org/ro-crate/1.1/structure.html :

It is RECOMMENDED that any referenced contextual entities are also described in the RO-Crate Metadata File with the same identifier. Similarly it is RECOMMENDED that any contextual entity in the RO-Crate Metadata file is linked to from at least one of the other entities using the same identifier.

ro-crate-py does not load referenced entities that are not described in the file, so the author list can include basic strings as well as Person objects. The same applies to organizations.

[elichad]

This should probably be transferred to https://github.com/ResearchObject/ro-crate-inveniordm but I first need to check if it faces the same issues