Show rejected broadcasts on ‘Previous alerts’ page

Two reasons to not hide rejected broadcasts:
- if a broadcast was rejected by mistake then it’s useful to have an
  audit of who did that
- it means you can still see old broadcasts without having to leave
  in pending-approval, which is dangerous because they might
  accidentally be approved

app/main/views/broadcast.py

@@ -48,7 +48,11 @@ def broadcast_dashboard(service_id):
 def broadcast_dashboard_previous(service_id):
     return render_template(
         'views/broadcast/previous-broadcasts.html',
-        broadcasts=BroadcastMessages(service_id).with_status('cancelled', 'completed'),
+        broadcasts=BroadcastMessages(service_id).with_status(
+            'cancelled',
+            'completed',
+            'rejected',
+        ),
         empty_message='You do not have any previous alerts',
         view_broadcast_endpoint='.view_previous_broadcast',
     )

app/templates/views/broadcast/partials/dashboard-table.html

@@ -18,6 +18,10 @@
             <p class="govuk-body govuk-!-margin-bottom-0 govuk-hint">
               Waiting for approval
             </p>
+          {% elif item.status == 'rejected' %}
+            <p class="govuk-body govuk-!-margin-bottom-0 govuk-hint">
+              Rejected {{ item.updated_at|format_datetime_relative }}
+            </p>
           {% elif item.status == 'broadcasting' %}
             <p class="govuk-body govuk-!-margin-bottom-0 live-broadcast">
               Live since {{ item.starts_at|format_datetime_relative }}