title: Access to Apollo server for NestJS GraphQL test
body: <p>A standard way to test an Apollo GraphQL server is to use the <a href="https://www.apollographql.com/docs/apollo-server/features/testing#createtestclient" rel="noreferrer">Apollo test client</a>.
  The <code>createTestClient</code> method requires a <code>server</code> argument.
  In a NestJS/TypeGraphQL application, what's the appropriate way to access the Apollo server that's created by <code>GraphQLModule</code> from inside a (Jest) test?</p>