User Rename fails for Delegated Directories created before an upgrade to Crowd 2.7 (Null external_id)

Steps to Reproduce

1. Create a Delegated Directory in Crowd pre-2.7 (e.g. Crowd 2.5.2). Make sure that the Synchronise User Details checkbox is checked, otherwise, the user rename feature will fail no matter what (not related to this bug)
2. Login with a couple of users in the delegated directory (so that their accounts are created in the cwd_user table)
3. Shutdown Crowd
4. Upgrade to Crowd 2.7 (tested with the in-place database upgrade method)
5. Run the following query in the Crowd Database:

   SELECT * FROM cwd_user WHERE user_name = '<username>';
   

   Replace <username> with the user that is affected. Notice that their external_id is NULL (which is why this bug occurs).

6. Rename the user in the LDAP server itself
7. Login with the new username. If you check the cwd_user table now, you will notice that there are now 2 accounts created for the same user, 1 with the old username and 1 with the new username

Workaround

After the Crowd upgrade to Crowd 2.7 , make sure all users login to their accounts at least once, before you proceed to rename any of their usernames in the LDAP server, to avoid breaking Crowd and other Crowd-connected applications. Always check the following to see if there are any users left, with a NULL external_id:

SELECT * FROM cwd_user WHERE external_id IS NULL;

Suggestion

We need to have an upgrade task to force an external_id sync with the LDAP server during/immediately after the upgrade, for all users in the delegated directory