class ActiveStorage::Variant

which in turn will use this +service_call+ method for its redirection.
for a variant that points to the ActiveStorage::Representations::ProxyController or ActiveStorage::Representations::RedirectController,
Use url_for(variant) (or the implied form, like link_to variant or redirect_to variant) to get the stable URL

Returns the URL of the blob variant on the service. See ActiveStorage::Blob#url for details.

def url(expires_in: ActiveStorage.service_urls_expire_in, disposition: :inline)
  service.url key, expires_in: expires_in, disposition: disposition, filename: filename, content_type: content_type
end