title: Output array in Twig
body: <p>I trying to output an array from the database to the screen.
  In my entity:</p>
  
  <pre><code>/**
   * @ORM\Column(type="array", nullable=true)
   */
  private $category;
  </code></pre>
  
  <p>In my twig template:</p>
  
  <pre><code>{% for category in user.profile.category %}
      {{ category }}
  {% endfor %}
  </code></pre>
  
  <p>Error:  <code>Array to string conversion in ...</code></p>
  
  <p>Where is my mistake?</p>