title: MongoDB regex option 'u' (UTF-8)
body: <p>I build a regex and I tried to use it with MongoDB but I don't have the expected result because I don't know how to enable UTF-8 support.</p>
  
  <hr>
  
  <p>For example with the regex : <code>\b42\b</code><br>
  <a href="https://regex101.com/r/7wWuwo/1" rel="nofollow noreferrer">Example available here</a>  </p>
  
  <p><strong>Should match :</strong></p>
  
  <pre><code>42
  hello 42
  hello-42-
  </code></pre>
  
  <p><strong>Shouldn't match :</strong></p>
  
  <pre><code>été42 
  042
   4 2 
  </code></pre>
  
  <p>The tricky match is this one : <code>été42</code>, without UTF-8 option it match with the regex but shouldn't.</p>
  
  <hr>
  
  <p>The <a href="https://docs.mongodb.com/v3.2/reference/operator/query/regex/#op._S_options" rel="nofollow noreferrer">documentation</a> don't mention the usual <code>u</code> option. </p>
  
  <p>So actually my query is : </p>
  
  <pre><code>db.getCollection('collection_name').find(
  {
      'title' : { $regex : '\\b42\\b', $options: 'i'}
  });
  </code></pre>
  
  <p>I use MongoDB version 3.2 but this issue is the same with 3.4.</p>