The validated context a successfully redeemed authorization code yields.
Attesto.AuthorizationCode.redeem/4 returns this struct once the code's
expiry, redirect URI, PKCE verifier, and DPoP binding have all checked
out. The host reads it to mint the access token (and, if it issues one,
the refresh token): subject and scope become the token's sub and
scope, dpop_jkt (when present) becomes the access token's cnf.jkt,
and claims carries any host context that rode along from the
authorization request.
family_id
When the authorization request supplied a :family_id to
Attesto.AuthorizationCode.issue/3, it rides through to this struct so
the host can mint the refresh-token family with that id. Linking the
code to the family it spawns is what lets code-reuse detection revoke the
right descendants (OAuth 2.0 Security BCP §4.13): a store that tracks
reuse records this family_id at redemption and replays it if the code
is presented again. nil when no family id was supplied.