title: how can I create a managed Apollo federation gateway?
body: <p>I'm going nuts with this as it sounds so simple.</p>
  
  <p>I started from this project: <a href="https://github.com/apollographql/federation-demo" rel="nofollow noreferrer">https://github.com/apollographql/federation-demo</a>
  Then I created an account on <a href="https://engine.apollographql.com" rel="nofollow noreferrer">https://engine.apollographql.com</a> where I registered the different federated services.
  I've a ENGINE_API_KEY for the Gateway as well.</p>
  
  <p>Fantastic, I can see traffic registered in the Engine!</p>
  
  <p>The next step is apparently to remove the "serviceList" from the config object in the ApolloGateway constructor.
  When the gateway starts it gives the following message: 
  <code>When `serviceList` is not set, an Apollo Engine configuration must be provided.</code></p>
  
  <p>What shall I do? What is an <em>"Apollo Engine configuration"</em> and how can I provide it?</p>