VCR: Make VC validators pluggable (and not hardcoded)

[reinkrul]

We have hardcoded validators for NutsAuthorizationCredentials and NutsOrganizationCredentials (and a base validator for any credential). These VC-type-specific validators shouldn't be hardcoded into the Nuts Node: it makes introducing new versions (through releasing a new JSON-LD context version) error-prone and unpractical, because it requires a Nuts Node released.

Validating VC types is a good feature to prevent (hard to debug) mistakes, but the validation rules should be externalized, so they become configuration of the Nuts Node, rather than hardcoded functionality.

Options:

• Don't do validation (the lazy solution)
• JSON schema (might be weird to combine with JSON-LD)
• Make own format (future compatibility issue/lots of work)
• ...?

[woutslakhorst]

Won't fix. Issuers are responsible and if self issued then the authorization policy should do it.