FEATURE: Add email normalization rules setting (PR #14593)

This setting can be used to block use of same email address through aliases. For example, for some email providers adding dots to the email address is just an alias. Another alias example is adding +STRING after the email username.

Normalization rules can be used to remove all dots and +STRING parts of an email.

GitHub

I think we should be doing only 1 sql query when normalize_emails is enabled

Seems weird to be storing the normalized emails for everyone when the setting defaults to off