title: Make custom variable in Django Context permanent
body: <p>I'm creating a website which has "categories" as a model in Django. To generate the sidebar, I iterate the categories and create a link for each one, which allows my to make it dinamic. </p>
  
  <p>The issue is that with the current approach, I have to put <code>Categories.objects.all()</code> as a variable in the context on every view, and I'm sure this is not the correct approach. How should I do to set <code>categories</code> as a context variable for any future View?  </p>