Merge accounts and change usernames.

Just as the summary suggests. It would be great if we could merge accounts and change usernames.

Here is why we need this:
Accounts are added and removed all the time. It would be great to merge accounts so that the data ownership belongs to person that is active.

Username changes happen all the time, especially when people get married.

We are currently migrating several users from ldap to active directory. Unfortunately we have to de-activate there ldap account and create a brand new account for active directory. This becomes really messy, since we have several deactivated accounts where the user is active in another account. It would be nice if we can merge accounts.