Create a OAuth2Auth provider for OpenID Connect Discovery. The discovery will use the given site in the
configuration options and attempt to load the well known descriptor.
If the discovered config includes a json web key url, it will be also fetched and the JWKs will be loaded
into the OAuth provider so tokens can be decoded.
vertx - the vertx instance
config - the initial config, it should contain a site url
handler - the instantiated Oauth2 provider instance handler