FEATURE: Implement 2factor login TOTP

implemented review items.

Blocking previous codes - valid 2-factor auth tokens can only be authenticated once/30 seconds.
I played with updating the “last used” any time the token was attempted but that seemed to be overkill, and frustrating as to why a token would fail.
Translatable texts.
Move second factor logic to a helper class.
Move second factor specific controller endpoints to its own controller.
Move serialization logic for 2-factor details in admin user views.
Add a login ember component for de-duplication
Fix up code formatting
Change verbiage of google authenticator

add controller tests:
second factor controller tests
change email tests
change password tests
admin login tests

add qunit tests - password reset, preferences

fix: check for 2factor on change email controller
fix: email controller - only show second factor errors on attempt
fix: check against 'true' to enable second factor.

Add modal for explaining what 2fa with links to Google Authenticator/FreeOTP

add two factor to email signin link

rate limit if second factor token present

add rate limiter test for second factor attempts

app/models/user_history.rb

@@ -66,7 +66,8 @@ class UserHistory < ActiveRecord::Base
                           change_name: 48,
                           post_locked: 49,
                           post_unlocked: 50,
-                          check_personal_message: 51)
+                          check_personal_message: 51,
+                          disabled_second_factor: 52)
   end
 
   # Staff actions is a subset of all actions, used to audit actions taken by staff users.
@@ -110,7 +111,8 @@ class UserHistory < ActiveRecord::Base
                         :backup_destroy,
                         :post_locked,
                         :post_unlocked,
-                        :check_personal_message]
+                        :check_personal_message,
+                        :disabled_second_factor]
   end
 
   def self.staff_action_ids