Verify Enveloped Credentials and Enveloped Presentations

[jrhender]

Partially addresses #424 . The objective of the PR is to add support for verifying application/vc and application/vp requests.

Two changes in the PR:

1. Adjusts respect-oas.js to support request schemas with multiple content-types. The UI change at the moment is that the text before each of the request schema tables is appended with "... with content-type header set to application/json", for example "The /presentations/verify endpoint uses the following schema when receiving a POST with content-type header set to application/json:". I'm open to adjusting this if folks have a different rendering preference.

2. Adds application/vc and application/vp schemas for POST /credentials/verify and POST /presentations/verify respectively

[msporny]

The group discussed this on the 2025-02-25 call and found that we do not expect application/vc or application/vp to be posted instead of application/json, but do expect oneOf the JSON Schemas listed to be used. The media type for the request will only ever be application/json with different schemas used when VCs or VPs are POSTed.

The PR needs to be updated so that the application/vc or application/vp media types aren't allowed for posting, only application/json and any of the schemas should be possible (based on the call being made).

[msporny]

The endpoints will receive application/json always -- any use of application/vc or application/vp are not allowed (even though VCs or VPs posted inside the JSON body are allowed/expected)