Add term and @id for serviceEndpoint

[PatStLouis]

Addresses this issue.

Let me know if this reflects what we discussed.

Additionally, do we want to also include the following endpoints in the description?

      - https://platform.example/organization/123/credentials/status
      - https://platform.example/organization/123/presentations

I can bundle this into this pr.

@nissimsan @mkhraisha

[brownoxford]

Does this fix the issue you are seeing when you test locally with the new traceability-v1.jsonld? I notice that the document still contains the empty context for TraceabilityAPI:

       "TraceabilityAPI": {
           "@id": "https://w3id.org/traceability#TraceabilityAPI",
           "@context": {}
       },

and also that serviceEndpoint is already defined in https://www.w3.org/ns/did/v1.

[PatStLouis]

@brownoxford @mkhraisha please be aware of this pr on the pyld repository and feel free to chime in, we found a bug in the library which was evaluating empty contexts as null values, as is indicated by section 5.1 of the json-ld expansion algorithm. An additional review would be welcome!

[mkhraisha]

Closed as resolved in a different library