JWT Auth Mixin

[PvanHengel]

Hi, This issue is for tracking the development of a new authentication mixin to support JWT token auth. Please post your comments on support for this here, I also have some sample code forked off with a potential solution for this.

https://github.com/PvanHengel/kernel_gateway/tree/feature/jwtmixin

Key requirements:

• inject decoded token into request object that notebook developers can use
• Openid connect well know auto configuration
• issuer and/or audience verification
• Jwks public key verification and cache ability for performance

Also as a bonus, would be ideal to have an option in the notebook itself for users that develop can do an oauth flow when not calling endpoints by api to inject the token into the notebook