Add the registered_user_id column to the admin UI.

templates/admin.html

@@ -48,6 +48,7 @@
     <div id="registeredUsers">
         <table>
             <thead>
+            <th>Matrix ID</th>
                 <th>User</th>
                 <th>Registration Time</th>
                 <th>Registration Code</th>
@@ -55,6 +56,7 @@
             <tbody>
                 {% for registered_user in registered_users %}
                     <tr>
+                        <td>{{ registered_user.registered_user_id|tojson|safe }}</td>
                         <td>{{ registered_user.username|tojson|safe }}</td>
                         <td>{{ registered_user.registered_time|tojson|safe }}</td>
                         <td>{{ registered_user.registration_code|tojson|safe }}</td>