Clarify how VC API is different from OID4

[msporny]

It was raised that we would need to clarify why/how VC API is different from OID4, namely that it's largely used for back-end credential management, machine-to-machine/unattended server-to-server workflows (with some effort), capable of running OID4* protocols over its exchanges, and not needing existing OID4 infrastructure to operate. VC API defines "primitives behind the scenes" -- for components that can be swapped out for doing entire lifecycle of credential issuance and verification, not strictly focused on deliver/exchange of credentials, it provides components for that process. Delivery/exchange mechanisms are compatible w/ OID4 -- you can use OID4 on top of VC API Exchange to do actual delivery.

[TallTed]

Please replace "namely that it's" with "namely that VC API is", and "It defines" with "VP API defines", in the initial comment above.

The antecedent of each is unclear, as the comment stands.

[msporny]

The group discussed this on 2024-03-12.

For the PR, we want:

• A new section titled "Relationship to OID4VCI and OID4VP"
• The new section should mention that the VC API handles credential lifecycle tasks that issuers, holders, and verifiers need to do beyond just credential pickup and presentation (such as issuing, status list management, holding and deriving, and verification)
• The VC API also supports OID4VCI and OID4VP, which can be build on top of the workflows and exchanges primitives provided by the VC API. That is OID4* (VCI + VP) are protocols that can be run on top of VC API exchanges, everything else the VC API provides communication between coordinators and services, etc. not communication between digital wallets and issuer/verifiers.

[wes-smith]

The group discussed this on 2024-04-30.

We noted the relationship to an open PR adding workflow and exchange support, and the PR to resolve this issue should contain a pointer to a section in the above PR explaining the power in VC API exchanges being agnostic to what delivery protocols run on top of them.