Use Prisma models as backing type

[tafelnl]

I just found out about the rootTypes (backing type) feature: https://nexusjs.org/guides/schema#backing-types-in-nexus

It is a great feature! I have been missing this in other GraphQL frameworks.

Now I am curious if this could work together with Prisma models without re-declaring the Database model again. If the Prisma models can be used as a backing type, that would follow the DRY rules and make developing way easier.