Contact model changes (#184)

* move source id from contacts

* Fix contactInbox model name

* rubocop fix

* Fix rspec

db/migrate/20191027054756_create_contact_inboxes.rb

@@ -0,0 +1,15 @@
+class CreateContactInboxes < ActiveRecord::Migration[6.1]
+  def change
+    create_table :contact_inboxes do |t|
+      t.references :contact, foreign_key: true, index: true
+      t.references :inbox, foreign_key: true, index: true
+      t.string :source_id, null: false
+
+      t.timestamps
+    end
+    add_index :contact_inboxes, [:inbox_id, :source_id], :unique => true
+    add_index :contact_inboxes, [:source_id]
+    remove_column :contacts, :inbox_id, :integer
+    remove_column :contacts, :source_id, :integer
+  end
+end