* when ACTIVATE_AFTER_REGISTRATION set to True, user will be activated after registration, and no email sending;
* when ACTIVATE_AFTER_REGISTRATION set to False, and REGISTRAION_SEND_EMAIL set to True, user will be activated by email;
* when ACTIVATE_AFTER_REGISTRATION set to False, and REGISTRAION_SEND_EMAIL set to Flase, user will be activated by admin.