Give platform admin users visibilty of API pages

Platform admins should be able to see what’s going on with a service’s
API integration, including:
- messages sent
- contents of whitelist
- names of keys

They should also be able to revoke keys in an emergency.

The only thing they _shouldn’t_ be able to do is create new keys
(because then they’d be able to send messages as the service).

app/templates/main_nav.html

@@ -57,7 +57,7 @@
   {% elif current_user.has_permissions(['view_activity']) %}
     <li><a href="{{ url_for('.manage_users', service_id=current_service.id) }}">Team members</a></li>
   {% endif %}
-  {% if current_user.has_permissions(['manage_api_keys']) %}
+  {% if current_user.has_permissions(['manage_api_keys'], admin_override=True) %}
     <li><a href="{{ url_for('.api_integration', service_id=current_service.id) }}">API integration</a></li>
   {% endif %}
   </ul>