title: Update ApolloClient headers after it was initialised
body: <p>My app is wrapped with <code>&lt;Apollo /&gt;</code> component that essentially initialises the client.</p>
  
  <pre><code>const client = new ApolloClient({
    link: new HttpLink({
      // ...
    }),
    cache: new InMemoryCache({
      // ..
    }),
  });
  </code></pre>
  
  <p>Further down the road users can make certain action that requires me to set few new headers to apollo client that were not there before. I initially thought to use react context for this to pass set new headers and consume them inside <code>&lt;Apollo /&gt;</code> but am not sure if this is the right way to go about it.</p>
  
  <p>After looking through the docs, it seems that apollo headers can be only set when it is initialised?</p>