Mechanism to request claims in JWT access tokens

[jbasney]

In WLCG we have:

• https://github.com/WLCG-AuthZ-WG/common-jwt-profile/blob/master/profile.md#scope-based-attribute-selection
• https://github.com/WLCG-AuthZ-WG/common-jwt-profile/blob/master/profile.md#group-based-capability-selection

There's also the OAuth 2.0 Rich Authorization Requests method:

• https://datatracker.ietf.org/doc/rfc9396/