Add first version of admin bulk change

app/controllers/repp/v1/domains/admin_contacts_controller.rb

@@ -0,0 +1,40 @@
+module Repp
+  module V1
+    module Domains
+      class AdminContactsController < BaseController
+        before_action :set_current_contact, only: [:update]
+        before_action :set_new_contact, only: [:update]
+
+        def set_current_contact
+          @current_contact = current_user.registrar.contacts.find_by!(code: contact_params[:current_contact_id])
+        end
+
+        def set_new_contact
+          @new_contact = current_user.registrar.contacts.find_by!(code: params[:new_contact_id])
+        end
+
+        def update
+          @epp_errors ||= []
+          @epp_errors << { code: 2304, msg: 'New contact must be valid' } if @new_contact.invalid?
+
+          unless @new_contact.identical_to?(@current_contact)
+            @epp_errors << { code: 2304, msg: 'Admin contacts must be identical' }
+          end
+
+          return handle_errors if @epp_errors.any?
+
+          affected, skipped = AdminDomainContact.replace(@current_contact, @new_contact)
+          @response = { affected_domains: affected, skipped_domains: skipped }
+          render_success(data: @response)
+        end
+
+        private
+
+        def contact_params
+          params.require(%i[current_contact_id new_contact_id])
+          params.permit(:current_contact_id, :new_contact_id)
+        end
+      end
+    end
+  end
+end