Display error message when toggling auto-renew from frontend fails

Problem

Follow-up to https://gitlab.com/gitlab-org/customers-gitlab-com/-/issues/10163

The above issue prevents admins impersonating customers from completing purchases (including turning auto renew on and off). Auto renew can be toggled from the subscription's additional actions dropdown from the subscriptions list page.

Toggle auto renew from subscription list

For handling auto renew toggle errors, we need to either

1. Decide how to show errors on the list page
   • a notice at the top of page or just at the top of subscription card?
2. Redirect to subscription show page and show the error there
   • should be easier & the success path is also redirected to subscription show page

Subscription show page