[Bug] Fix conversation assignment mailer url (#374)

* Fix conversation assignment mailer url

* Remove mailer scope

app/views/assignment_mailer/conversation_assigned.html.erb

@@ -2,4 +2,4 @@
 
 <p>Time to save the world. A new conversation has been assigned to you</p>
 
-<p>Click <%= link_to 'here', conversation_url(id: @conversation.display_id) %> to get cracking. </p>
+<p>Click <%= link_to 'here', app_conversation_url(id: @conversation.display_id) %> to get cracking. </p>

config/routes.rb

@@ -13,7 +13,7 @@ Rails.application.routes.draw do
 
   resources :widgets, only: [:index]
 
-  namespace :api, :defaults => { :format => 'json' } do
+  namespace :api, defaults: { format: 'json' } do
     namespace :v1 do
       resources :callbacks, only: [] do
         collection do
@@ -83,11 +83,11 @@ Rails.application.routes.draw do
           end
         end
       end
-
     end
   end
 
-  scope module: 'mailer' do
+  # Used in mailer templates
+  resource :app, only: [:index] do
     resources :conversations, only: [:show]
   end