[UX]: Login link to an nonexistent resource flow

[mountainash]

When following a link like https://getcockpit.dev/cockpit/auth/login?to=/pages/page/657725a21f796d45730a9612 (from an email or IM), if your session is expired, you'll get a login screen. When you attempt to login... the following error shows briefly, and then shows the login form again (even though correct login details were given). This leaves the user is a confused state, where a login screen is shown, yet you can't login. If you don't see the URL, you aren't aware of why - also if you then manually change the URL to https://getcockpit.dev/cockpit/auth/ you'll get a 404

Requested resource is not available

Options:

• the error can be missed [scrolled down on a small screen, slow connection, etc.] (make it stay until the user dismisses it)
• log the user in, create a session
• [suggested UX] load the dashboard (then show the error)
• add a redirect to /auth/login from /auth(/)? if the user session doesn't exist, else redirect to the default logged in URL [Dashboard?]