One-time state for an OpenID Connect authorization transaction.
Transactions bind the callback to the issuer, client, redirect URI, nonce,
PKCE verifier, and opaque initiating browser-session value that created it.
They are deliberately stored behind the
AttestoClient.AuthorizationTransaction.Store behaviour so applications can
choose storage appropriate to their topology. The included ETS store is
suitable for a single node; clustered deployments should provide a store
with equivalent atomic put_new and take semantics.
A transaction contains protocol secrets, especially the PKCE verifier and browser binding. Never send it to the browser or log it.