title: How can one get a complete GraphQL schema from an Apollo Server endpoint?
body: <p>I'm writing a GraphQL interface between GraphQL and REST services using Apollo Server. This interface will provide a single GraphQL endpoint for an Apollo Client front.  </p>
  
  <p>The single service at the moment is a KeystoneJS app which provides a GraphQL endpoint, through (as far as I know) Apollo Server.  To keep things simple for the moment, I'm downloading the GraphQL schema from the KeystoneJS server GraphQL Playground and using it as my interface's GraphQL schema (after removing definitions that Keystone generates and Apollo Server doesn't understand).</p>
  
  <p>I'd like to automate this process -- that is, somehow 'grab' the GraphQL schema that KeystoneJS/Apollo Server generates, just as if I were to download it from the GraphQL Playground.  Is there a way to do this from the endpoint? (I don't want to touch the KeystoneJS internals, just access the schema through the endpoint)</p>