Details of `DELETE /credentials/{id}` endpoint should be added

[laysakura]

https://w3c-ccg.github.io/vc-api/#issuer-service includes DELETE /credentials/{id} but any detailed API spec is not written.

[msporny]

The group discussed this on the 2024-07-23 telecon:

The specification clearly does not document the DELETE /credentials/{id} endpoint and needs to do so.

A PR should be raised that:

• Adds a section to the specification that covers the DELETE /credentials/{id} endpoint in both the Issuer Service and the Holder Service.
• Explain why the DELETE service is needed for "right to be forgotten".

[msporny]

PR #491 has been merged to address this issue, closing.