[Feature] Email collect message hooks (#331)

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

spec/actions/contact_merge_action_spec.rb

@@ -9,9 +9,7 @@ describe ::ContactMergeAction do
 
   before do
     2.times.each { create(:conversation, contact: base_contact) }
-    2.times.each { create(:contact_inbox, contact: base_contact) }
     2.times.each { create(:conversation, contact: mergee_contact) }
-    2.times.each { create(:contact_inbox, contact: mergee_contact) }
   end
 
   describe '#perform' do