Add display and claim metadata

[danielfett]

This PR adds the display and claim metadata as defined in the Type Metadata draft (with minor changes).

Note that this includes the "claim verification metadata" and "claim selective disclosure metadata", where there were some discussions around the requirements and mechanisms to use. I left them in here to foster a discussion, but we can also split them out into separate PRs.

Rendered version: https://drafts.oauth.net/oauth-sd-jwt-vc/danielfett/fix-224-add-display-metadata/draft-ietf-oauth-sd-jwt-vc.html

[awoie]

We had to remove the display feature language in the schema PR for consistency reasons and because we didn't want to suggest features are included that are in fact not there yet. So, this PR should re-introduce the language in the type metadata intro:

, and how they can be displayed.

[bc-pi]

We had to remove the display feature language in the schema PR for consistency reasons and because we didn't want to suggest features are included that are in fact not there yet. So, this PR should re-introduce the language in the type metadata intro:

, and how they can be displayed.

https://github.com/oauth-wg/oauth-sd-jwt-vc/pull/231/files#r1661453204 and https://github.com/oauth-wg/oauth-sd-jwt-vc/pull/231/files#diff-e750c0958ca10e395b4d3b77bb5aafccc668b4a1a50675dda79a8d90b39a2468L494 are where that happened or will happen

[bc-pi]

please update the language tag approach to reflect the rough consensus achieved briefly in the room (where you were not present) at IETF 120

[bc-pi]

Request changes sorry... but the issuer isn't always the owner of the type metadata

[bc-pi]

some nit picky suggestions but overall lgtm