incorrect Drupal 8 login URL
If you create a public contribution page on a Drupal 8 site, it will include a login link for unauthenticated users, with parameters
?destination=... to direct back to the contribution page after login. This link is broken with recent Drupal versions, because it needs to go to /user/login instead of just /user.
I have a fix in my branch; will post the PR.