Add Domain#transfer

app/models/domain.rb

@@ -672,6 +672,11 @@ class Domain < ActiveRecord::Base
     pending_json['new_registrant_id']
   end
 
+  def transfer(new_registrar)
+    self.registrar = new_registrar
+    regenerate_auth_info
+  end
+
   def self.to_csv
     CSV.generate do |csv|
       csv << column_names
@@ -705,5 +710,11 @@ class Domain < ActiveRecord::Base
   def self.uses_zone?(zone)
     exists?(["name ILIKE ?", "%.#{zone.origin}"])
   end
+
+  private
+
+  def regenerate_auth_info
+    generate_auth_info!
+  end
 end
 # rubocop: enable Metrics/ClassLength

test/models/domain_test.rb

@@ -0,0 +1,16 @@
+require 'test_helper'
+
+class DomainTest < ActiveSupport::TestCase
+  def setup
+    @domain = domains(:shop)
+  end
+
+  def test_transfers_domain
+    old_auth_info = @domain.auth_info
+    new_registrar = registrars(:goodnames)
+    @domain.transfer(new_registrar)
+
+    assert_equal new_registrar, @domain.registrar
+    refute_same @domain.auth_info, old_auth_info
+  end
+end