Support DC API

[leifj]

Problem Statement

The wwWallet should support the DC API.

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Proposed Solution (Optional)

Minimally we need to support the response_mode dc_api.jwt which is more or less direct_post.jwt
Optionally we should think about also supporting direct parameter passing for openid4vp in addition to JAR

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Additional Information (Optional)

Related to #928 however the response handling shouldn't have to care where the DC API is running.

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[leifj]

It is probably a good idea to add DC API support (using JAR requests) to the ACME test verifier at the same time.