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).

test/unit/dmail_test.rb

@@ -18,7 +18,7 @@ class DmailTest < ActiveSupport::TestCase
     context "that is spam" do
       should "be automatically reported and deleted" do
         @recipient = create(:user)
-        @spammer = create(:user, created_at: 2.weeks.ago, email: "akismet-guaranteed-spam@example.com")
+        @spammer = create(:user, created_at: 2.weeks.ago, email_address: build(:email_address, address: "akismet-guaranteed-spam@example.com"))
 
         SpamDetector.stubs(:enabled?).returns(true)
         dmail = create(:dmail, owner: @recipient, from: @spammer, to: @recipient, creator_ip_addr: "127.0.0.1")
@@ -87,14 +87,14 @@ class DmailTest < ActiveSupport::TestCase
     end
 
     should "send an email if the user wants it" do
-      user = create(:user, receive_email_notifications: true)
+      user = create(:user, receive_email_notifications: true, email_address: build(:email_address))
       assert_difference("ActionMailer::Base.deliveries.size", 1) do
         create(:dmail, to: user, owner: user, body: "test [[tagme]]")
       end
     end
 
     should "create only one message for a split response" do
-      user = FactoryBot.create(:user, :receive_email_notifications => true)
+      user = create(:user, receive_email_notifications: true, email_address: build(:email_address))
       assert_difference("ActionMailer::Base.deliveries.size", 1) do
         Dmail.create_split(from: CurrentUser.user, creator_ip_addr: "127.0.0.1", to_id: user.id, title: "foo", body: "foo")
       end

test/unit/spam_detector.rb

@@ -7,7 +7,7 @@ class SpamDetectorTest < ActiveSupport::TestCase
       SpamDetector.stubs(:enabled?).returns(true)
 
       @user = create(:gold_user, created_at: 1.month.ago)
-      @spammer = create(:user, created_at: 2.weeks.ago, email: "akismet-guaranteed-spam@example.com")
+      @spammer = create(:user, created_at: 2.weeks.ago, email_address: build(:email_address, address: "akismet-guaranteed-spam@example.com"))
     end
 
     context "for dmails" do

test/unit/user_deletion_test.rb

@@ -27,13 +27,13 @@ class UserDeletionTest < ActiveSupport::TestCase
 
   context "a valid user deletion" do
     setup do
-      @user = create(:user, email: "ted@danbooru.com")
+      @user = create(:user, email_address: build(:email_address))
       @deletion = UserDeletion.new(@user, "password")
     end
 
     should "blank out the email" do
       @deletion.delete!
-      assert_nil(@user.reload.email)
+      assert_nil(@user.reload.email_address)
     end
 
     should "rename the user" do