Add an option to update (midPoint user) attribute value when account is deleted

Scenario: e-mail address is generated while provisioning to mail server, fetched via inbound and stored in user/emailAddress attribute.
If the mail server account is deleted, the e-mail address is still stored in user, which can be ok or can be confusing, because other user can later get the same address when provisioned to mail server.

Maybe there should be an explicit option in mappings, to remove the value (or send empty value or something) when the account is deleted.
It could even be used to set an arbitrary value to user attribute when the account is deleted...