refactor: Studio OAuth cleanup, part 1 (#28760)

- Update migration instructions
    - Changes regarding redirect URLs and cookie domain are to permit the
      site to run on multiple domains.
- Set LOGIN_URL in common so that it can be unset in environment overrides

This bypasses the "redirect to LMS" login/signup code, but does not yet
remove it; removal is covered by DEPR-166 so that this remains a
configuration-only change for now.

There should have no user-visible effect.

ref: ARCHBOM-1890

cms/djangoapps/contentstore/tests/tests.py

@@ -181,7 +181,7 @@ class AuthTestCase(ContentStoreTestCase):
             )
             self.assertContains(
                 response,
-                '<a class="action action-signin" href="/signin_redirect_to_lms?next=http%3A%2F%2Ftestserver%2F">'
+                '<a class="action action-signin" href="/login/?next=http%3A%2F%2Ftestserver%2F">'
                 'Sign In</a>'
             )
 

cms/envs/common.py

@@ -647,11 +647,8 @@ LMS_INTERNAL_ROOT_URL = LMS_ROOT_URL
 # Use LMS SSO for login, once enabled by setting LOGIN_URL (see docs/guides/studio_oauth.rst)
 SOCIAL_AUTH_STRATEGY = 'auth_backends.strategies.EdxDjangoStrategy'
 LOGIN_REDIRECT_URL = EDX_ROOT_URL + '/home/'
-# TODO: Set LOGIN_URL to '/login/' after Studio OAuth transition is complete, and
-# finish ARCH-1253 cleanup. See docs/guides/studio_oauth.rst
-LOGIN_URL = reverse_lazy('login_redirect_to_lms')
-FRONTEND_LOGIN_URL = lambda settings: settings.LMS_ROOT_URL + '/login'
-derived('FRONTEND_LOGIN_URL')
+LOGIN_URL = '/login/'
+FRONTEND_LOGIN_URL = LOGIN_URL
 # Warning: Must have trailing slash to activate correct logout view
 # (auth_backends, not LMS user_authn)
 FRONTEND_LOGOUT_URL = '/logout/'

cms/envs/devstack.py

@@ -48,9 +48,6 @@ LMS_BASE = 'localhost:18000'
 LMS_ROOT_URL = f'http://{LMS_BASE}'
 FEATURES['PREVIEW_LMS_BASE'] = "preview." + LMS_BASE
 
-# TODO: Remove after Studio OAuth transition is complete. See docs/guides/studio_oauth.rst
-LOGIN_URL = '/login/'
-FRONTEND_LOGIN_URL = LMS_ROOT_URL + '/login'
 FRONTEND_REGISTER_URL = LMS_ROOT_URL + '/register'
 ########################### PIPELINE #################################