[Feature] Email collect message hooks (#331)

- Add email collect hook on creating conversation
- Merge contact if it already exist

spec/factories/inboxes.rb

@@ -3,7 +3,11 @@
 FactoryBot.define do
   factory :inbox do
     account
-    name { 'Inbox' }
     channel { FactoryBot.build(:channel_widget, account: account) }
+    name { 'Inbox' }
+
+    after(:create) do |inbox|
+      inbox.channel.save!
+    end
   end
 end