feat: Add moderations create api (#3020)

# What does this PR do?
This PR adds Open AI Compatible moderations api. Currently only
implementing for llama guard safety provider
Image support, expand to other safety providers and Deprecation of
run_shield will be next steps.


## Test Plan
Added 2 new tests for safe/ unsafe text prompt examples for the new open
ai compatible moderations api usage
`SAFETY_MODEL=llama-guard3:8b LLAMA_STACK_CONFIG=starter uv run pytest
-v tests/integration/safety/test_safety.py
--text-model=llama3.2:3b-instruct-fp16
--embedding-model=all-MiniLM-L6-v2 --safety-shield=ollama`
(Had some issue with previous PR
https://github.com/meta-llama/llama-stack/pull/2994 while updating and
accidentally close it , reopened new one )

llama_stack/core/routers/safety.py

@@ -10,6 +10,7 @@ from llama_stack.apis.inference import (
     Message,
 )
 from llama_stack.apis.safety import RunShieldResponse, Safety
+from llama_stack.apis.safety.safety import ModerationObject, OpenAICategories
 from llama_stack.apis.shields import Shield
 from llama_stack.log import get_logger
 from llama_stack.providers.datatypes import RoutingTable
@@ -60,3 +61,41 @@ class SafetyRouter(Safety):
             messages=messages,
             params=params,
         )
+
+    async def run_moderation(self, input: str | list[str], model: str) -> ModerationObject:
+        async def get_shield_id(self, model: str) -> str:
+            """Get Shield id from model (provider_resource_id) of shield."""
+            list_shields_response = await self.routing_table.list_shields()
+
+            matches = [s.identifier for s in list_shields_response.data if model == s.provider_resource_id]
+            if not matches:
+                raise ValueError(f"No shield associated with provider_resource id {model}")
+            if len(matches) > 1:
+                raise ValueError(f"Multiple shields associated with provider_resource id {model}")
+            return matches[0]
+
+        shield_id = await get_shield_id(self, model)
+        logger.debug(f"SafetyRouter.run_moderation: {shield_id}")
+        provider = await self.routing_table.get_provider_impl(shield_id)
+
+        response = await provider.run_moderation(
+            input=input,
+            model=model,
+        )
+        self._validate_required_categories_exist(response)
+
+        return response
+
+    def _validate_required_categories_exist(self, response: ModerationObject) -> None:
+        """Validate the ProviderImpl response contains the required Open AI moderations categories."""
+        required_categories = list(map(str, OpenAICategories))
+
+        categories = response.results[0].categories
+        category_applied_input_types = response.results[0].category_applied_input_types
+        category_scores = response.results[0].category_scores
+
+        for i in [categories, category_applied_input_types, category_scores]:
+            if not set(required_categories).issubset(set(i.keys())):
+                raise ValueError(
+                    f"ProviderImpl response is missing required categories: {set(required_categories) - set(i.keys())}"
+                )