Feature: Add ability to disable auto assignment of conversations (#513)

db/migrate/20200217192734_add_enable_auto_assignment_to_inboxes.rb

@@ -0,0 +1,5 @@
+class AddEnableAutoAssignmentToInboxes < ActiveRecord::Migration[6.0]
+  def change
+    add_column :inboxes, :enable_auto_assignment, :boolean, default: true
+  end
+end