Made admin link only display for non expired registration codes

templates/admin.html

@@ -24,7 +24,10 @@
                         <td>{{ registration_code.expiration_time|tojson|safe }}</td>
                         <td>{{ registration_code.usages|tojson|safe }}</td>
                         <td>{{ registration_code.max_usages|tojson|safe }}</td>
-                        <td><a href="/register?registrationCode={{ registration_code.code }}">link</a>
+                        <td>
+                            {% if not registration_code.is_expired() %}
+                            <a href="/register?registrationCode={{ registration_code.code }}">link</a>
+                            {% endif %}
                         <td>
                             <form method="POST" action="/admin/expire_registration_code">
                                 <input type="hidden" name="csrf_token" value="{{ csrf_token() }}"/>