title: Emit deprecation warnings with Apollo client
body: <h1>Background</h1>
  
  <p>We are working on a fairly large <a href="https://www.apollographql.com/" rel="nofollow noreferrer">Apollo</a> project. A very simplified version of our api looks like this:</p>
  
  <pre class="lang-apollo prettyprint-override"><code>type Operation {
      foo: String
      activity: Activity
  }
  
  type Activity {
      bar: String
      # Lots of fields here ...
  }
  </code></pre>
  
  <p>We've realised splitting <code>Operation</code> and <code>Activity</code> does no benefit and adds complexity. We'd like to merge them. But there's a lot of queries that assume this structure in the code base. In order to make the transition gradual we add <code>@deprecated</code> directives:</p>
  
  <pre class="lang-apollo prettyprint-override"><code>type Operation {
      foo: String
      bar: String
      activity: Activity @deprecated
  }
  
  type Activity {
      bar: String @deprecated(reason: "Use Operation.bar instead")
      # Lots of fields here ...
  }
  </code></pre>
  
  <h1>Actual question</h1>
  
  <p>Is there some way to highlight those deprecations going forward? Preferably by printing a warning in the browser console when (in the test environment) running a query that uses a deprecated field?</p>