Broaden context for "control-panel-page-expired"

[caseydwyer]

Not sure if the 419 behavior still happens, but I stumbled onto something similar where you're just stuck in an infinite auth cycle—completing the form with valid credentials loops you back to the login page via a couple of 302 redirects, with no context. The solution listed on this troubleshooting page solved it, though (user_id must be a varchar) so felt like it made sense as an addition here, instead of a whole new page.