feat: make object registration idempotent (#3752)

# What does this PR do?

objects (vector dbs, models, scoring functions, etc) have an identifier
and associated object values.

we allow exact duplicate registrations.

we reject registrations when the identifier exists and the associated
object values differ.

note: model are namespaced, i.e. {provider_id}/{identifier}, while other
object types are not

## Test Plan

ci w/ new tests

llama_stack/core/routing_tables/common.py

@@ -9,7 +9,6 @@ from typing import Any
 from llama_stack.apis.common.errors import ModelNotFoundError
 from llama_stack.apis.models import Model
 from llama_stack.apis.resource import ResourceType
-from llama_stack.apis.scoring_functions import ScoringFn
 from llama_stack.core.access_control.access_control import AccessDeniedError, is_action_allowed
 from llama_stack.core.access_control.datatypes import Action
 from llama_stack.core.datatypes import (
@@ -17,6 +16,7 @@ from llama_stack.core.datatypes import (
     RoutableObject,
     RoutableObjectWithProvider,
     RoutedProtocol,
+    ScoringFnWithOwner,
 )
 from llama_stack.core.request_headers import get_authenticated_user
 from llama_stack.core.store import DistributionRegistry
@@ -114,7 +114,7 @@ class CommonRoutingTableImpl(RoutingTable):
             elif api == Api.scoring:
                 p.scoring_function_store = self
                 scoring_functions = await p.list_scoring_functions()
-                await add_objects(scoring_functions, pid, ScoringFn)
+                await add_objects(scoring_functions, pid, ScoringFnWithOwner)
             elif api == Api.eval:
                 p.benchmark_store = self
             elif api == Api.tool_runtime:

llama_stack/core/store/registry.py

@@ -96,9 +96,11 @@ class DiskDistributionRegistry(DistributionRegistry):
 
     async def register(self, obj: RoutableObjectWithProvider) -> bool:
         existing_obj = await self.get(obj.type, obj.identifier)
-        # dont register if the object's providerid already exists
-        if existing_obj and existing_obj.provider_id == obj.provider_id:
-            return False
+        if existing_obj and existing_obj != obj:
+            raise ValueError(
+                f"Object of type '{obj.type}' and identifier '{obj.identifier}' already exists. "
+                "Unregister it first if you want to replace it."
+            )
 
         await self.kvstore.set(
             KEY_FORMAT.format(type=obj.type, identifier=obj.identifier),