We need to do both. Per our internal discussion, the P0 is to provide the raw token, as the developer can parse it themselves. The raw token is needed, as some API may require passing the whole id_token as is.
Getting all of the claims is a more intrusive change. The right way to do the latter is to ensure that all properties are calculated instead of static strings. As such copy constructor and serialization will change. The whole class and a lot of tests will have to be modified. I can do it as a second pull request.