Support RFC 9493 ("sub_id" claim)

[OrangeDog]

Expected Behavior

RFC 9493 defines the "sub_id" claim for transmitting typed subject identifiers, rather than relying on the flat string of "sub".

Support for this at the Resource and Authroization servers would be very helpful, similar to the SAML ID support.

Current Behavior

Manually parsing and serialising the structures and string constants from/to the Map<String, Object> of claims.

Context

Identifying users that may have multiple identifiers, federating across domains that may have identifier conflicts, etc.