Merge pull request #5511 from yakky/feature/apphook_config_multisite_31

Removed globally unique constraint for Apphook configs

cms/admin/forms.py

@@ -288,6 +288,7 @@ def __init__(self, *args, **kwargs):
     def _check_unique_namespace_instance(self, namespace):
         return Page.objects.filter(
             publisher_is_draft=True,
+            site_id=self.instance.site_id,
             application_namespace=namespace
         ).exclude(pk=self.instance.pk).exists()