two more docs todo

howto/puppet.md

@@ -904,6 +904,15 @@ hours.
 This configuration is in `/etc/cron.d/puppet-crontab` and deployed by
 Puppet itself, currently as part of the `torproject_org` module.
 
+### LDAP integration
+
+TODO: document how Puppet talks with LDAP (and vice-versa?).
+
+### External data sources
+
+TODO: document which parts of Puppet come from external entities. I
+know of at least NRPE and Let's encrypt, but there could be others?
+
 ## Issues
 
 There is no issue tracker specifically for this project, [File][] or