DID, minimal implementation of Walt.id with existing next-auth setup

[Sébastien Palluel]

## General links

• https://blog.iota.org/login-with-iota-walt-id/
• https://docs.walt.id/
• https://walt.id/blog/p/idp-kit

Walt.id API

https://wallet.walt.id/api/swagger

Follow specs of OpenID Connect for integration as provider in Next Auth:

• https://openid.net/connect/

• example of OIDC provider implementation with next auth: nextauthjs/next-auth#250 (comment)

• Doc for OIDC provider provider implementation: https://next-auth.js.org/configuration/providers/oauth#client-option

  #### TODO:

• federated logout: nextauthjs/next-auth#3938 (comment)