Save last login method in a cookie (#12286)

Initial attempt to save the "last login method" into a cookie so we can
show a visual label next to the button to login.

This is only the backend part. We need to write some code in the
template to use this value next.

I'm not happy with the implementation because looks pretty complex. I
didn't find an easier way to do it and I'm open for suggestions.

Required by readthedocs/ext-theme#421

Author: humitos

readthedocs/profiles/views.py

@@ -3,8 +3,10 @@
 from enum import StrEnum
 from enum import auto
 
+import structlog
 from allauth.account.views import LoginView as AllAuthLoginView
 from allauth.account.views import LogoutView as AllAuthLogoutView
+from allauth.socialaccount import providers
 from allauth.socialaccount.providers.github.provider import GitHubProvider
 from django.conf import settings
 from django.contrib import messages
@@ -52,8 +54,29 @@
 from readthedocs.projects.utils import get_csv_file
 
 
+log = structlog.get_logger(__name__)
+
+
 class LoginViewBase(AllAuthLoginView):
-    pass
+    def get_context_data(self, **kwargs):
+        context_data = super().get_context_data(**kwargs)
+        last_login_method = self.request.COOKIES.get("last-login-method")
+        context_data["last_login_method"] = last_login_method
+
+        last_login_tab = "vcs"  # Default tab"
+        if last_login_method == "email":
+            last_login_tab = "email"
+        if last_login_method in providers.registry.provider_map.keys():
+            last_login_tab = "vcs"
+        if last_login_method == "sso":
+            last_login_tab = "sso"
+        log.debug(
+            "Login method.",
+            last_login_method=last_login_method,
+            last_login_tab=last_login_tab,
+        )
+        context_data["last_login_tab"] = last_login_tab
+        return context_data
 
 
 class LoginView(SettingsOverrideObject):