Finally, there is a solution @Theo Stolker .
If I parse by URL and send parameters "resolveFully=true" and "validateExternalRefs=true", the specification is fully resolved including external references.  I can't commit\push this update directly, because if a user puts a URL only accessible from inside his organization, It does not work.  It's not really a problem because the validator tools can be run locally in a container, but I have to update the documentation too.
I created the related issue 9 to follow the progression.  I can't continue anymore this morning.  I'll continue this evening.

Thank you very much for your contribution @Theo Stolker .
Your pull request is merged and a new release on OEX has been published.  

I'm still wondering if there is a simple way to resolve external references, I'll check if something help with validator.swagger.io (this tools is already used by OpenAPI suite).  There is an option for external ref but I don't know yet what that implies, I have to test that.

Hi @Theo Stolker ,

I just tested the "DID Manager" specification.

With the simple http client, I noticed a code generation issue with double-quoted HTTP status code.
It's fixed.

I see a generated model like model.CompoundServicePropertiesserviceEndpoint empty.
So, If we check the specification and we can see:

        serviceEndpoint:
          description: A map containing service references and/or endpoints.
          example: { 'auth': 'did:nuts:EwVMYK2ugaMvRHUbGFBhuyF423JuNQbtpes35eHhkQic/serviceEndpoint?type=auth' }
          type: object

It's a type object, but there is no schema defined, so we can't generate any properties in this case.
This is the same problem with the model model.OrganizationSearchResultorganization.

I also noticed external references in the specification file like :

        didDocument:
          $ref: '../common/ssi_types.yaml#/components/schemas/DIDDocument'

Indeed, this case is not supported.
I haven't checked for all the specs, but I think the 2 cases noted are the cause for the empty models.

If we specify a URL, maybe it would be possible to download the external ref and load the definition (to analyze...).