Include DEFAULT_AUTHENTICATION_CLASSES when token auth is disabled

When TOKEN_AUTH_DISABLED=True, ContainerRegistryApiMixin only used
RegistryAuthentication (Basic auth), ignoring any custom backends
configured in DEFAULT_AUTHENTICATION_CLASSES.

Now includes both RegistryAuthentication and all configured default
authentication classes, allowing deployments to use custom auth
backends alongside standard Basic auth for container registry
operations.

Fixes #2362

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 2 people

CHANGES/2362.feature

@@ -0,0 +1,3 @@
+When token auth is disabled, container registry API views now include
+DEFAULT_AUTHENTICATION_CLASSES alongside RegistryAuthentication, allowing
+deployments to use custom authentication backends.

pulp_container/app/registry_api.py

@@ -230,9 +230,14 @@ class ContainerRegistryApiMixin:
     def authentication_classes(self):
         """
         List of authentication classes to check for this view.
+
+        When token auth is disabled, includes both RegistryAuthentication (Basic auth)
+        and any authentication classes configured in DEFAULT_AUTHENTICATION_CLASSES.
+        This allows deployments to use custom authentication backends (e.g. remote
+        header-based auth) alongside standard Basic auth for container registry operations.
         """
         if settings.get("TOKEN_AUTH_DISABLED", False):
-            return [RegistryAuthentication]
+            return [RegistryAuthentication, *api_settings.DEFAULT_AUTHENTICATION_CLASSES]
         return [TokenAuthentication]
 
     @property