[OID4VP] Verifier Configuration API in the Cloud Agent

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](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html#section-9)

The REST API should expose the Verifier Metadata (example can be found in the [Verifier Metadata](https://openid.net/specs/openid-4-verifiable-presentations-1_0.html#name-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:
```json
{
"vp_formats": {
"vc+sd-jwt": {
"sd-jwt_alg_values": ["ES256", "ES384"],
"kb-jwt_alg_values": ["ES256", "ES384"]
}
}
}
```