Code-first approach using classes with decorators as a single source of truth

From https://github.com/MichalLytek/typegraphql-prisma/issues/1#issue-714873665:
> And in the near feature - when Prisma SDK will be ready - the `typegraphql-prisma` integration will also allow to use a code-first approach to build a `schema.prisma` and GraphQL schema at once, using classes with decorators as a single source of truth. Stay tuned! 💪

Are we there yet? Is the Prisma SDK ready? If not, what exactly is missing?

Recently I've been chatting with @divyenduz and he asked to open issue(s) about this in Prisma repo(s), so the Prisma team would have them in mind.

Start by reviewing the Prisma SDK status and the existing code-first discussion linked in the issue. Identify what would be required for classes with decorators to generate both schema.prisma and the GraphQL schema, and record which SDK capabilities are still missing. Done means the status and scope are clearly documented.

Written by the indexing model from the issue text.