title: Select AuthGuard type on the fly
body: <p>My app will use two different auth strategies - one for users using a browser and another for the <em>public</em> API. I'll set a <code>header</code> for those using a browser, and then my app will set the auth strategy based on the value of that <code>header</code>.</p>
  
  <p>I have set up the two auth strategies, and given them names. I can now do this in my controller methods:</p>
  
  <pre><code>@Get()
  @UseGuards(AuthGuard('strategy_name'))
  async find() { }
  </code></pre>
  
  <p>What I would like to do, is NOT have to specify the auth guard type next to every controller method, nor the logic for determining which type to use. Instead, I'd like to put this logic in one place, which will be read by ALL calls to <code>AuthGuard()</code>.</p>
  
  <p>What's the best way to do this? Is there some kind of filter/hook/interceptor for <code>AuthGuard</code>?  </p>