fix: Don't show Billings on settings navbar when self-hosted (#1912)

* Do not show billing settings navbar item when self hosted

* Do not show billing settings navbar item when self hosted

* Add condition to settings helper

* Let Stripe::AuthenticationError bubble up

test/controllers/subscriptions_controller_test.rb

@@ -1,7 +1,14 @@
 require "test_helper"
 
 class SubscriptionsControllerTest < ActionDispatch::IntegrationTest
-  # test "the truth" do
-  #   assert true
-  # end
+  setup do
+    sign_in @user = users(:family_admin)
+  end
+
+  test "redirects to settings if self hosting" do
+    Rails.application.config.app_mode.stubs(:self_hosted?).returns(true)
+    get subscription_path
+    assert_redirected_to root_path
+    assert_equal I18n.t("subscriptions.self_hosted_alert"), flash[:alert]
+  end
 end