Feature: Implement OpenID Connect

[tvanhens]

Implementing the OpenID Connect spec on top of the existing OAuth v2 implementation would allow openauth consumers to use their deployment as an identity source for applications which support OIDC as an identity source.

Examples of integrations this would open up are:

• Auth for AWS Elastic Load Balancing
• Access Control for API Gateway

Because OIDC is an extension on top of OAuth v2 this could be implemented as an additional opt-in layer for appropriate issuers.

[tanayvk]

https://github.com/openauthjs/openauth/blob/master/packages/openauth/src/provider/oidc.ts - there's an oidc provider already

[tvanhens]

That provider is an authentication provider, it doesn't allow openauth to behave as an oidc issuer.

[sam-goodwin]

Working on an implementation over here: https://github.com/sam-goodwin/openauth

Have made some additional changes to embed it as a submodule in my SST app's repo while i work out the final details. Once its stable for my use-case, i'll work on a PR to contribute it back.