title: Is the content of a const std::optional always const?
body: <p>I would assume </p>
  
  <pre><code>std::optional&lt;const std::string&gt;
  </code></pre>
  
  <p>allows to assign a new value to the optional, but it is not possible to change the string itself and in</p>
  
  <pre><code>const std::optional&lt;const std::string&gt;
  </code></pre>
  
  <p>it is not possible to do both. But what about the following?</p>
  
  <pre><code>const std::optional&lt;std::string&gt;
  </code></pre>