users: move emails to separate table.

* Move emails from users table to email_addresses table.
* Validate that addresses are formatted correctly and are unique across
  users. Existing invalid emails are grandfathered in.
* Add is_verified flag (the address has been confirmed by the user).
* Add is_deliverable flag (an undeliverable address is an address that bounces).
* Normalize addresses to prevent registering multiple accounts with the
  same email address (using tricks like Gmail's plus addressing).

app/logical/email_normalizer.rb

@@ -0,0 +1,76 @@
+module EmailNormalizer
+  module_function
+
+  IGNORE_DOTS = %w[gmail.com]
+  IGNORE_PLUS_ADDRESSING = %w[gmail.com hotmail.com outlook.com live.com]
+  IGNORE_MINUS_ADDRESSING = %w[yahoo.com]
+  CANONICAL_DOMAINS = {
+    "googlemail.com" => "gmail.com",
+    "hotmail.co.uk" => "outlook.com",
+    "hotmail.co.jp" => "outlook.com",
+    "hotmail.co.th" => "outlook.com",
+    "hotmail.com" => "outlook.com",
+    "hotmail.ca" => "outlook.com",
+    "hotmail.de" => "outlook.com",
+    "hotmail.es" => "outlook.com",
+    "hotmail.fr" => "outlook.com",
+    "hotmail.it" => "outlook.com",
+    "live.com.au" => "outlook.com",
+    "live.com.ar" => "outlook.com",
+    "live.com.mx" => "outlook.com",
+    "live.co.uk" => "outlook.com",
+    "live.com" => "outlook.com",
+    "live.ca" => "outlook.com",
+    "live.cl" => "outlook.com",
+    "live.cn" => "outlook.com",
+    "live.de" => "outlook.com",
+    "live.fr" => "outlook.com",
+    "live.it" => "outlook.com",
+    "live.jp" => "outlook.com",
+    "live.nl" => "outlook.com",
+    "live.se" => "outlook.com",
+    "msn.com" => "outlook.com",
+    "yahoo.com.au" => "yahoo.com",
+    "yahoo.com.ar" => "yahoo.com",
+    "yahoo.com.br" => "yahoo.com",
+    "yahoo.com.cn" => "yahoo.com",
+    "yahoo.com.hk" => "yahoo.com",
+    "yahoo.com.mx" => "yahoo.com",
+    "yahoo.com.ph" => "yahoo.com",
+    "yahoo.com.sg" => "yahoo.com",
+    "yahoo.com.tw" => "yahoo.com",
+    "yahoo.com.vn" => "yahoo.com",
+    "yahoo.co.id" => "yahoo.com",
+    "yahoo.co.kr" => "yahoo.com",
+    "yahoo.co.jp" => "yahoo.com",
+    "yahoo.co.uk" => "yahoo.com",
+    "yahoo.ca" => "yahoo.com",
+    "yahoo.cn" => "yahoo.com",
+    "yahoo.de" => "yahoo.com",
+    "yahoo.es" => "yahoo.com",
+    "yahoo.fr" => "yahoo.com",
+    "yahoo.it" => "yahoo.com",
+    "ymail.com" => "yahoo.com",
+    "126.com" => "163.com",
+    "aim.com" => "aol.com",
+    "gmx.com" => "gmx.net",
+    "gmx.at" => "gmx.net",
+    "gmx.ch" => "gmx.net",
+    "gmx.de" => "gmx.net",
+    "gmx.fr" => "gmx.net",
+    "gmx.us" => "gmx.net",
+  }
+
+  def normalize(address)
+    return nil unless address.count("@") == 1
+
+    name, domain = address.downcase.split("@")
+
+    domain = CANONICAL_DOMAINS.fetch(domain, domain)
+    name = name.delete(".") if domain.in?(IGNORE_DOTS)
+    name = name.gsub(/\+.*\z/, "") if domain.in?(IGNORE_PLUS_ADDRESSING)
+    name = name.gsub(/-.*\z/, "") if domain.in?(IGNORE_MINUS_ADDRESSING)
+
+    "#{name}@#{domain}"
+  end
+end

app/logical/spam_detector.rb

@@ -12,7 +12,7 @@ class SpamDetector
 
   attr_accessor :record, :user, :user_ip, :content, :comment_type
   rakismet_attrs author: proc { user.name },
-                 author_email: proc { user.email },
+                 author_email: proc { user.email_address&.address },
                  blog_lang: "en",
                  blog_charset: "UTF-8",
                  comment_type: :comment_type,

app/logical/user_deletion.rb

@@ -29,7 +29,7 @@ class UserDeletion
   end
 
   def clear_user_settings
-    user.email = nil
+    user.email_address = nil
     user.last_logged_in_at = nil
     user.last_forum_read_at = nil
     user.favorite_tags = ''

app/logical/user_email_change.rb

@@ -8,11 +8,10 @@ class UserEmailChange
   end
 
   def process
-    if User.authenticate(user.name, password).nil?
-      user.errors[:base] << "Password was incorrect"
+    if User.authenticate(user.name, password)
+      user.update(email_address_attributes: { address: new_email })
     else
-      user.email = new_email
-      user.save
+      user.errors[:base] << "Password was incorrect"
     end
   end
 end