Add comments to app.ini about external source synchronization job

Author: lafriks

conf/app.ini

@@ -441,7 +441,12 @@ OLDER_THAN = 24h
 
 ; Synchronize external user data (only LDAP user synchronization is supported)
 [cron.sync_external_users]
+; Syncronize external user data when starting server (default false)
+RUN_AT_START = false
+; Interval as a duration between each synchronization (default every 24h)
 SCHEDULE = @every 24h
+; Create new users, update existing user data and disable users that are not in external source anymore (default)
+;   or only create new users if UPDATE_EXISTING is set to false
 UPDATE_EXISTING = true
 
 [git]