outposts: re-add _config for backwards compat

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

authentik/outposts/api/outposts.py

@@ -18,6 +18,8 @@ class OutpostSerializer(ModelSerializer):
     """Outpost Serializer"""
 
     config = JSONField(validators=[is_dict], source="_config")
+    # TODO: Remove _config again, this is only here for legacy with older outposts
+    _config = JSONField(validators=[is_dict], read_only=True)
     providers_obj = ProviderSerializer(source="providers", many=True, read_only=True)
 
     def validate_config(self, config) -> dict:
@@ -40,6 +42,7 @@ class OutpostSerializer(ModelSerializer):
             "service_connection",
             "token_identifier",
             "config",
+            "_config",
         ]