FIX: return 429 when admin api key is limited on admin route

This also handles a general case where exceptions leak out prior to being handled by the application controller

spec/requests/email_controller_spec.rb

@@ -5,7 +5,6 @@ RSpec.describe EmailController do
     describe 'when email is invalid' do
       it 'should return the right response' do
         get '/email/unsubscribed', params: { email: 'somerandomstring' }
-
         expect(response.status).to eq(404)
       end
     end