Support for the IBM task in Keycloak

[Ogenbertrand]

Description

This EPIC is going to track every issue/task we pick from the IBM milestone.

• [OID4VCI] Generate pre-authorized codes using the JWT format #237
• [OID4VCI] CredentialSignerException: Proof Type null is not supported for format ldp_vc #238

[Ogenbertrand]

Main EPIC from keycloak: keycloak#43936