The same config used for beginAuthorization.
The state/nonce/codeVerifier persisted at login start.
The full redirect URL the issuer returned to.
Injectable fetch (defaults to the global).
Optionalinit: RequestInitOptionalinit: RequestInitOptionalinit: RequestInitInjectable clock in epoch seconds (for tests).
The validated TokenSet.
The caller must delete the pending state from storage before calling this so a replayed callback can never reuse the verifier (PKCE single-use, docs/24-sdk-design.md D3). Most integrations should use createUpbond instead.
AuthError on issuer error, missing/invalid callback, state mismatch, a failed token request, or id_token validation failure.
Complete a login: validate the callback against the stored PendingAuthorization, exchange the code at the token endpoint, and validate the returned id_token's binding claims (issuer, audience, expiry, nonce, subject).