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/functional/maintenance/user/email_changes_controller_test.rb

@@ -5,7 +5,7 @@ module Maintenance
     class EmailChangesControllerTest < ActionDispatch::IntegrationTest
       context "in all cases" do
         setup do
-          @user = create(:user, :email => "bob@ogres.net")
+          @user = create(:user, email_address: build(:email_address, { address: "bob@ogres.net" }))
         end
 
         context "#new" do
@@ -20,16 +20,14 @@ module Maintenance
             should "work" do
               post_auth maintenance_user_email_change_path, @user, params: {:email_change => {:password => "password", :email => "abc@ogres.net"}}
               assert_redirected_to(edit_user_path(@user))
-              @user.reload
-              assert_equal("abc@ogres.net", @user.email)
+              assert_equal("abc@ogres.net", @user.reload.email_address.address)
             end
           end
 
           context "with the incorrect password" do
             should "not work" do
               post_auth maintenance_user_email_change_path, @user, params: {:email_change => {:password => "passwordx", :email => "abc@ogres.net"}}
-              @user.reload
-              assert_equal("bob@ogres.net", @user.email)
+              assert_equal("bob@ogres.net", @user.reload.email_address.address)
             end
           end
         end