SignInResult

JWT token — also set as the auth HttpOnly cookie.

Content locale the freshly minted session carries: the language the visitor was explicitly browsing in while signed out, falling back to the account's saved default language. Null when no cookie session was established (embed business-pinned tokens, re-redeeming while already signed in) or when the session carries no locale claim. Clients should apply it live so the UI switches to the signed-in user's language without a reload.