Revert "Support custom authentication backends"

This reverts merge request !334 (merged).

The way custom authentication backends were implemented break too much stuff, or requires workarounds that hide other mistakes. As nothing in AlekSIS uses custom auth backends, and we are currently integratin django-allauth in !413 (merged), I request the feature to be removed.

If someone wants to add a custom authentication backend, they should hook into allauth instead.

@hansegucker Please merge after taking note if you do not have any objective arguments to keep this custom implementation.

Closes #313 (closed)

aleksis/core/apps.py

@@ -2,8 +2,6 @@ from typing import Any, List, Optional, Tuple
 
 import django.apps
 from django.apps import apps
-from django.conf import settings
-from django.db import OperationalError, ProgrammingError
 from django.http import HttpRequest
 from django.utils.module_loading import autodiscover_modules
 
@@ -16,7 +14,7 @@ from .registries import (
     site_preferences_registry,
 )
 from .util.apps import AppConfig
-from .util.core_helpers import get_site_preferences, has_person
+from .util.core_helpers import has_person
 from .util.sass_helpers import clean_scss
 
 
@@ -52,8 +50,6 @@ class CoreConfig(AppConfig):
         preference_models.register(personpreferencemodel, person_preferences_registry)
         preference_models.register(grouppreferencemodel, group_preferences_registry)
 
-        self._refresh_authentication_backends()
-
         self._load_data_checks()
 
         from .health_checks import DataChecksHealthCheckBackend
@@ -70,24 +66,6 @@ class CoreConfig(AppConfig):
             data_checks += getattr(model, "data_checks", [])
         DataCheckRegistry.data_checks = data_checks
 
-    @classmethod
-    def _refresh_authentication_backends(cls):
-        """Refresh config list of enabled authentication backends."""
-        from .preferences import AuthenticationBackends  # noqa
-
-        idx = settings.AUTHENTICATION_BACKENDS.index("django.contrib.auth.backends.ModelBackend")
-
-        try:
-            # Don't set array directly in order to keep object reference
-            settings._wrapped.AUTHENTICATION_BACKENDS.clear()
-            settings._wrapped.AUTHENTICATION_BACKENDS += settings.ORIGINAL_AUTHENTICATION_BACKENDS
-
-            for backend in get_site_preferences()["auth__backends"]:
-                settings._wrapped.AUTHENTICATION_BACKENDS.insert(idx, backend)
-                idx += 1
-        except (ProgrammingError, OperationalError):
-            pass
-
     def preference_updated(
         self,
         sender: Any,
@@ -97,9 +75,6 @@ class CoreConfig(AppConfig):
         new_value: Optional[Any] = None,
         **kwargs,
     ) -> None:
-        if section == "auth" and name == "backends":
-            self._refresh_authentication_backends()
-
         if section == "theme":
             if name in ("primary", "secondary"):
                 clean_scss()