Key attestation methods

[peppelinux]

I read here

https://github.com/vcstuff/high-assurance-profile/blob/main/draft-high-assurance-profile-oid4vc-sd-jwt-vc.md#issuer-identification-and-key-resolution-to-validate-an-issued-credential-issuer-key-resolution

that only x509 and .well-known/jwt-issuer MUST be supported

At the same time I have the "perception" that Federation has a higher level for the attestation of requirements and keys, since it brings metadata, policy and custom attestations (trust marks), and that todate we don't have clear requirements to compare x509 or .well-known/jwt-issuer more or less high.

Since this new specification is dedicated to the High profile, I think it is appropriate to do a PR to obtain the JWS trust_chain header parameter within this new profile

[Sakurann]

closing as a duplicate of #119, since that one encompasses this one