Link to callbacks from inbound page

If you’ve got an inbound number and are using the API you’ll probably
be interested in this new feature we’ve got. And if you do know about
it, you might not be able to find it because we’ve moved it.

app/templates/views/service-settings/set-inbound-sms.html

@@ -19,6 +19,12 @@
           If you want to turn this feature off,
           <a href="{{ url_for('.support') }}">get in touch with the GOV.UK Notify team</a>.
         </p>
+        {% if current_user.has_permissions(['manage_api_keys'], admin_override=True) %}
+          <p>
+            You can set up callbacks for received text messages on the
+            <a href="{{ url_for('.api_callbacks', service_id=current_service.id) }}">API integration page</a>.
+          </p>
+        {% endif %}
       {% else %}
         <p>
           Receiving text messages from your users is an