Contact model changes (#184)

* move source id from contacts

* Fix contactInbox model name

* rubocop fix

* Fix rspec

app/models/contact_inbox.rb

@@ -0,0 +1,8 @@
+class ContactInbox < ApplicationRecord
+  validates :inbox_id, presence: true
+  validates :contact_id, presence: true
+  validates :source_id, presence: true
+
+  belongs_to :contact
+  belongs_to :inbox
+end