[OID4VP] Verifier Configuration API in the Cloud Agent

[yshyn-iohk]

This issue is a subtask of the hyperledger/identus/issues/16
According to the OID4VP specification, the Verifier (cloud-agent) should expose the Verifier Metadata

The REST API should expose the Verifier Metadata (example can be found in the Verifier Metadata apendix of the spec)

It would be nice to configure these metadata dynamically (per tenant), but for simplicity, they might be static values in the configuration file.

Example:

{
  "vp_formats": {
    "vc+sd-jwt": {
      "sd-jwt_alg_values": ["ES256", "ES384"],
      "kb-jwt_alg_values": ["ES256", "ES384"]
    }
  }
}