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

Gemfile.lock

@@ -73,6 +73,7 @@ GEM
       uniform_notifier (~> 1.10.0)
     byebug (9.0.6)
     certified (1.0.0)
+    chunky_png (1.3.8)
     coderay (1.1.2)
     concurrent-ruby (1.0.5)
     connection_pool (2.2.1)
@@ -298,6 +299,9 @@ GEM
       redis (~> 3.0, >= 3.0.4)
     request_store (1.3.2)
     rinku (2.0.2)
+    rotp (3.3.0)
+    rqrcode (0.10.1)
+      chunky_png (~> 1.0)
     rspec (3.6.0)
       rspec-core (~> 3.6.0)
       rspec-expectations (~> 3.6.0)
@@ -479,6 +483,8 @@ DEPENDENCIES
   redis
   redis-namespace
   rinku
+  rotp
+  rqrcode
   rspec
   rspec-html-matchers
   rspec-rails