Two templates necessary in order to customize the login page

Problem/Motivation

The login page currently is displayed at two different paths: /user and /user/login. As a result it's necessary to supply two different templates in order to customize the whole page: page--user.html.twig and page--user--login.html.twig. However the former will also be picked up when rendering the user profile.

The attachment lt.tar.gz contains the stark theme with those two templates added.

/user as seen by anonymous user:

/user/login as seen by anonymous user:

/user/X as seen by authenticated user:

Proposed resolution

Remove the login form from /user and always redirect to user/login as suggested in #2294571: Redirect anonymous users to login page from an exception listener instead of in MaintenanceModeSubscriber and restrict access to the my-account link to authenticated users.

Remaining tasks

User interface changes

API changes