client_id_scheme doesn't support Federation

[peppelinux]

In https://vcstuff.github.io/oid4vc-haip-sd-jwt-vc/draft-oid4vc-haip-sd-jwt-vc.html#section-5-1.5

I read

client_id_scheme value MUST be either x509_san_dns or verifier_attestation. Wallet MUST support both. Verifier MUST support at least one. (pending OID4VCI PR #524 for verifier_attestation)

this is not compatible with the italian implementation that uses OIDC Federation, with a value of "entity_id"
we ask to extend this configuration using a wider approach

let's consider that for interop purpose both federation and x509 are used, this parameter is exclusive

[Sakurann]

can we please first agree that we want to support OIDC.Fed in HAIP? None of the extension points of OID4VC in HAIP support OIDC.Fed because there is no such agreement. and for the reasons I stated in Issue #59, I am reluctant to add OIDC.Fed right now.

[Sakurann]

duplicate of #88.
once we agree to add federation, this will be addressed. closing for now to focus the discussion on #88