How to configure OpenID Connect Userinfo endpoint


I need to connect ot an Open ID Connect implementation that doesn’t put username by default within the ID-token. The attributes are available at a specific userinfo endpoint. How can I access this from ShinyProxy or, if that is not possible how can I manipulate the request in order to ask for attributes (claimns) within the ID-token.

Google for instance does put a claim like email in the ID-token by default, but how to deal with implementation that do not do this?