Expose ZBD Login API endpoints to zbd/node SDK

## Tasks

- Ingest the ZBD Login OAuth2 API endpoints and expose them to this SDK
- Aim to abstract away the complexities of the API and provide easy-to-use function calls for the API

### Resources

- https://docs.zebedee.io/docs/zbd-login/intro
- https://docs.zebedee.io/api/oauth2/authorization