title: PYQgis - add border to legend
body: <p>I would just like to add a black border of 1mm to my legend generated with PYQgis.</p>
  <p>Like this (with QGis):
  <a href="https://i.stack.imgur.com/keltP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/keltP.png" alt="enter image description here" /></a></p>
  <p>How can I do ?</p>
  <p>Here is my code :</p>
  <pre><code># LEGENDE
  legend = QgsLayoutItemLegend(layout)
  
  # STYLE LEGENDE (https://qgis.org/pyqgis/3.10/core/QgsLegendStyle.html)
  legend.setStyleFont(QgsLegendStyle.Title, QFont('Lucida Fax', 18))
  legend.setStyleFont(QgsLegendStyle.Subgroup, QFont('Lucida Fax', 13, QFont.Bold))
  legend.setStyleFont(QgsLegendStyle.SymbolLabel, QFont('Lucida Fax', 11))
  </code></pre>
  <p>Thank you</p>