add examples for batch_credential_issuance & other credential metadata parameters

[jogu]

We don't seem to have an example metadata that includes batch_credential_issuance - we probably should as example really help people see how things are used and where they sit in the structure.

[c2bo]

The same seems to hold true for

• credential_request_encryption
• credential_response_encryption
• batch_credential_issuance

Should we add one larger example of credential issuer metadata in the appendix with all of these options populated?

[jogu]

Good point. And actually I think it's even worse than that, there's not an example for any of the credential issuer metadata defined in https://openid.net/specs/openid-4-verifiable-credential-issuance-1_0-16.html#section-11.2.4 other than credential_configurations_supported!

An appendix sounds good to me.