Align data models to the VC Data Model

Created by: nissimsan

This issue stems from https://github.com/uncefact/spec-untp/pull/90

Several of our examples are based on an approach of essentially recreating the VC Data Model (which defines issuer, validFrom, etc..), with the intent to wrap that all into the credentialSubject of a VC. That will produce a quite inelegant data graph with a lot of duplication and potential for inconsistencies (issuer vs issuedBy, validFrom vs validFrom...).

Rather, we want to leverage the VCDM. For example issuer, should be added within a complex object instead of repeating it within the credentialSubject. For example:

... "issuer": { "@type": [ "Organization" ], "@id": "did:web:nis.example.com", "taxIdentificationNumnber": "DK-12345678", "name": "Nis Global Unltd.", "street": "Ocean Lane 100", "locality": "Paradise Island", "country": "DK" }, "credentialSubject": { "type": [ "ConformityStuff" ], "aClaim": "conforming", "anotherClaim": "legit", ...