Deleting a user keeps the users email unchanged

How to reproduce

• Create a user with a specific mail address
• Use the direct delete process to delete the user
• Still in usernamagement, open the list with all the deleted users (access rights, last menu item)
• User appears as deleted user
  => OK: username has been modified to contain a timestamp and a bpk prefix
  => NOK: the mail address is the old mail address from the identity

In older releases the mail address was modified in the same manner to not generate any "mail already in use" conflict

Now, when a user tries to connect via oAuth, the user can not be mapped due to the already existing identity

Query to search for those broken identities:

select id, name, user_id, u_email from o_bs_identity, o_user where u_email not like '%bkp%' and name like '%bkp%' and fk_user_id = user_id;

Side note
Probably caused by the flattened user properties.
However. Line 355 in UserDeletionManager seems fishy as well. IMHO keepUserEmailAfterDeletion should be keepUserLoginAfterDeletion