frontend: Add deletion buttons

crates/frontend/public/templates/pages/addressbook.html

@@ -10,4 +10,12 @@
 
 <pre>{{ addressbook|json }}</pre>
 
+<h2>Delete</h2>
+
+<section>
+  <form method="POST" action="/frontend/user/{{addressbook.principal}}/addressbook/{{addressbook.id}}/delete">
+    <button type="submit">Move to trash</button>
+  </form>
+</section>
+
 {% endblock %}