Are you looking for the ID Token or an Access Token? ID Tokens are always JWTs, however, Access Tokens can be opaque or a JWT depending on the audience.
The example looks like an Access Token, but it sounds like you are wanting user data.
You can use the Management API’s GET/api/v2/users/{id} endpoint to get user data. In order to make the request, you’ll need to get a Management API Access Token which you can see how to do here:
This is not what we are looking for. We looking for some api which can be called with the payload, private key and generate the JWT user assertion token. The steps which we do manually to produce from webui. Can we join a short call just to explain. This will add much more value to what we have here.