Deletes users from the native realm.
DELETE /_security/user/<username>
- 
username(required)
- 
  (string) An identifier for the user.
To use this API, you must have at least the manage_security cluster privilege.
The following example deletes the user jacknich:
DELETE /_security/user/jacknich
If the user is successfully deleted, the request returns {"found": true}.
Otherwise, found is set to false.