Improve candidate account creation using bulk create #499
Description
For https://github.com/compserv/hknweb/blob/master/hknweb/forms.py#L243
Currently each user creation is separate in a for loop, which is a single query per user, very slow. Try https://docs.djangoproject.com/en/4.1/ref/models/querysets/#bulk-create for bulk creation of users to speed this up to avoid timeout.