Feature Request: Expose the token issue and expiry.

[christopherbatih]

Checklist

• I've updated to the latest released version of the SDK
• I've searched for existing feature requests on GitHub issues
• I've read the Code of Conduct
• I've given my issue the title: Feature Request: [name of my feature request]

Goals

As the title suggests, I'd like to see the issue and expiry timestamps parsed into the AuthenticationToken class as publicly accessible fields; to allow for better session management and negate the need to parse the JWT ourselves to access the (already) parsed datas.