title: Generate GraphQL schema from TypeScript?
body: <p>I have just recently started with Apollo and would like to expose some existing REST APIs through a new GraphQL layer.</p>
  <p>These REST services are already <strong>fully</strong> (Request and Response data structures) covered by an extensive set of custom Typescript type definitions.</p>
  <p>I was hoping to find a way to re-use these existing types, and, maybe with a few additional <code>Query</code> types on top, be able to generate a GraphQL schema instead of duplicating the code.</p>
  <p>Surprisingly this appears to be a rather rare use case? I found many tools to generate Typescript definitions from GraphQL, but the reverse direction seems to be difficult.</p>
  <p><a href="https://typegraphql.com/docs/types-and-fields.html" rel="noreferrer">type-graphql</a> only works if all custom types are <code>class</code>es. That doesn't work for me; I don't have a <strong>single</strong> class but a myriad of simple <code>type</code>s here.</p>
  <p><a href="https://www.npmjs.com/package/ts2graphql" rel="noreferrer">ts2graphql</a> hasn't been updated in a year and I can't even get the example code to work.</p>
  <p>What else could I try?</p>