Allow disabling of new sign ups for tunnel admin user

Prior to this change, the internet exposed gitlab
instance would not restrict new user signups which
can pose as a security threat.

This change will add a security mechanism that
specs which run in the ssh tunnel could use to
disable new user signups

app/views/admin/application_settings/_signup.html.haml

@@ -4,7 +4,7 @@
   %fieldset
     .form-group
       .form-check
-        = f.check_box :signup_enabled, class: 'form-check-input'
+        = f.check_box :signup_enabled, class: 'form-check-input', data: { qa_selector: 'signup_enabled_checkbox' }
         = f.label :signup_enabled, class: 'form-check-label' do
           Sign-up enabled
           .form-text.text-muted

qa/qa/flow/sign_up.rb

@@ -37,6 +37,19 @@ module QA
 
         raise "Failed to register the user" unless success
       end
+
+      def disable_sign_ups
+        Flow::Login.sign_in_as_admin
+        Page::Main::Menu.perform(&:go_to_admin_area)
+        Page::Admin::Menu.perform(&:go_to_general_settings)
+
+        Page::Admin::Settings::General.perform do |general_settings|
+          general_settings.expand_sign_up_restrictions do |signup_settings|
+            signup_settings.disable_signups
+            signup_settings.save_changes
+          end
+        end
+      end
     end
   end
 end

qa/qa/page/admin/settings/component/sign_up_restrictions.rb

@@ -8,6 +8,7 @@ module QA
           class SignUpRestrictions < Page::Base
             view 'app/views/admin/application_settings/_signup.html.haml' do
               element :require_admin_approval_after_user_signup_checkbox
+              element :signup_enabled_checkbox
               element :save_changes_button
             end
 
@@ -15,6 +16,11 @@ module QA
               check_element :require_admin_approval_after_user_signup_checkbox
               click_element :save_changes_button
             end
+
+            def disable_signups
+              uncheck_element :signup_enabled_checkbox
+              click_element :save_changes_button
+            end
           end
         end
       end

qa/qa/scenario/test/integration/ssh_tunnel.rb

+# frozen_string_literal: true
+
+module QA
+  module Scenario
+    module Test
+      module Integration
+        class SSHTunnel < Test::Instance::All
+          tags :ssh_tunnel
+        end
+      end
+    end
+  end
+end