title: URL scheme, should put ID in url or in parameter?
body: <p>Suppose you want a url for books of a user</p>
  <p>You can do</p>
  <pre><code>   1. /book/{user_id}
     2. /user/{user_id}/books
     3. /book?user_id={user_id}
  </code></pre>
  <p>When to use each of the above and why?</p>