OID4VC: Ability to patch credential metadata

[timbl-ont]

The current API can create and delete credential metadata via the credential-supported endpoint. Each supported credential type is associated with a supported_cred_id which is used by the controller to issue a credential of that type.

Any updates of the metadata require a new entry (and old entry deleted) which changes the supported_cred_id. This then requires that the controller be updated and redeployed.

The addition of PATCH to the credential-supported endpoint would enable the updating of the metadata without changing the supported_cred_id. For simplicity it could be a wholesale replacement of the JSON configuration.