OptionalalgorithmSigning algorithm. Falls back to stone.auth.algorithm (default HS256).
OptionalaudienceAudience (aud). Falls back to stone.auth.audience.
OptionalexpiresLifetime, e.g. '1h', '15m', or seconds. Falls back to stone.auth.expiresIn.
OptionalissuerIssuer (iss). Falls back to stone.auth.issuer.
OptionalsubjectSubject (sub).
Options for signing a token.