/login path "Already authenticated" error

[aronmal]

Describe the bug
When already being logging in from a previous session, hitting the /login route and and logging in again result in a /error page with "Already authenticated"

To Reproduce
Steps to reproduce the behavior:

1. Login and close the tab
2. Go to /login and login
3. See "Already authenticated"

Expected behavior
A automatic redirect to the /accounts route should be possible and would be nice.

Just make a hit at the /user/login route and check if "Already authenticated" is the case and then auto redirect to /accounts when a user is opening /login by accident. (I had it as a bookmark by accident, changed it now to only be /)