Store a sealed OAuth2 authorization code.
Called by the serverless callback function after the browser redirect. The
``state`` carries BOTH the patron npub (the lookup/retrieve key) and the
operator npub (the PUBLIC key the code is sealed to) — see the SDK's
``pack_oauth_state``. The code is sealed with NIP-44 to the operator so only
that operator's nsec can open it; the Neon row is keyed by the patron npub,
so retrieval (``retrieve_code(state=patron_npub)``) is unchanged.
Args:
code: The authorization code from the OAuth provider.
state: The packed state (``patron_npub.operator_npub``).
Returns:
Dict with ``success`` key and a message.
Connector