Provide option to disallow changing Username on user edit form

I do use LDAP provisioning. Unfortunately, the username change does dot work properly! At least when you login as an LDAP user that has the "administer users" permission, but NOT the "change own username" permission.

If you then change your own username from - let's say user1 to user2, Drupal says the change was successful. The LDAP server in fact has changed the username properly. However, Drupal's "users" table then has both usernames stored, but you will only be able to login again with the old username. The LDAP sync gets messed up, and you have lost all your Drupal roles, maybe other information as well.

In short, changing the (at least own) username makes lots of trouble - maybe due to some bugs of LDAP provisioning. Untile these bugs get fixed, I think it would be easier to just give an option to disallow username change at all.

Renaming his own username also works fine on my environment when the user have granted the permissions administer ldap modules, choose roles for new accounts, create accounts, administer permissions and administer users.

However, when the user that renames his own username only have administer users from the above listed permissions, the problems arise. In that case, the authmap table's authname value did not get changed! After logging out, the user cannot login with the new username. The user table creates a new user with the new username, assigning a new uid. The old account with the original uid will be kept, but looses the roles.

And yes, I am using the latest dev versions of your modules.