chore!: Safety api refactoring to use OpenAIMessageParam (#3796)

# What does this PR do?
Remove usage of deprecated `Message` from Safety apis


## Test Plan
CI

llama_stack/providers/inline/safety/llama_guard/llama_guard.py

@@ -12,10 +12,9 @@ from typing import Any
 from llama_stack.apis.common.content_types import ImageContentItem, TextContentItem
 from llama_stack.apis.inference import (
     Inference,
-    Message,
     OpenAIChatCompletionRequestWithExtraBody,
+    OpenAIMessageParam,
     OpenAIUserMessageParam,
-    UserMessage,
 )
 from llama_stack.apis.safety import (
     RunShieldResponse,
@@ -165,7 +164,7 @@ class LlamaGuardSafetyImpl(Safety, ShieldsProtocolPrivate):
     async def run_shield(
         self,
         shield_id: str,
-        messages: list[Message],
+        messages: list[OpenAIMessageParam],
         params: dict[str, Any] = None,
     ) -> RunShieldResponse:
         shield = await self.shield_store.get_shield(shield_id)
@@ -175,8 +174,8 @@ class LlamaGuardSafetyImpl(Safety, ShieldsProtocolPrivate):
         messages = messages.copy()
         # some shields like llama-guard require the first message to be a user message
         # since this might be a tool call, first role might not be user
-        if len(messages) > 0 and messages[0].role != Role.user.value:
-            messages[0] = UserMessage(content=messages[0].content)
+        if len(messages) > 0 and messages[0].role != "user":
+            messages[0] = OpenAIUserMessageParam(content=messages[0].content)
 
         # Use the inference API's model resolution instead of hardcoded mappings
         # This allows the shield to work with any registered model
@@ -208,7 +207,7 @@ class LlamaGuardSafetyImpl(Safety, ShieldsProtocolPrivate):
             messages = [input]
 
         # convert to user messages format with role
-        messages = [UserMessage(content=m) for m in messages]
+        messages = [OpenAIUserMessageParam(content=m) for m in messages]
 
         # Determine safety categories based on the model type
         # For known Llama Guard models, use specific categories
@@ -277,7 +276,7 @@ class LlamaGuardShield:
 
         return final_categories
 
-    def validate_messages(self, messages: list[Message]) -> None:
+    def validate_messages(self, messages: list[OpenAIMessageParam]) -> list[OpenAIMessageParam]:
         if len(messages) == 0:
             raise ValueError("Messages must not be empty")
         if messages[0].role != Role.user.value:
@@ -288,7 +287,7 @@ class LlamaGuardShield:
 
         return messages
 
-    async def run(self, messages: list[Message]) -> RunShieldResponse:
+    async def run(self, messages: list[OpenAIMessageParam]) -> RunShieldResponse:
         messages = self.validate_messages(messages)
 
         if self.model == CoreModelId.llama_guard_3_11b_vision.value:
@@ -307,10 +306,10 @@ class LlamaGuardShield:
         content = content.strip()
         return self.get_shield_response(content)
 
-    def build_text_shield_input(self, messages: list[Message]) -> OpenAIUserMessageParam:
-        return OpenAIUserMessageParam(role="user", content=self.build_prompt(messages))
+    def build_text_shield_input(self, messages: list[OpenAIMessageParam]) -> OpenAIUserMessageParam:
+        return OpenAIUserMessageParam(content=self.build_prompt(messages))
 
-    def build_vision_shield_input(self, messages: list[Message]) -> OpenAIUserMessageParam:
+    def build_vision_shield_input(self, messages: list[OpenAIMessageParam]) -> OpenAIUserMessageParam:
         conversation = []
         most_recent_img = None
 
@@ -333,7 +332,7 @@ class LlamaGuardShield:
                     else:
                         raise ValueError(f"Unknown content type: {c}")
 
-                conversation.append(UserMessage(content=content))
+                conversation.append(OpenAIUserMessageParam(content=content))
             else:
                 raise ValueError(f"Unknown content type: {m.content}")
 
@@ -342,9 +341,9 @@ class LlamaGuardShield:
             prompt.append(most_recent_img)
         prompt.append(self.build_prompt(conversation[::-1]))
 
-        return OpenAIUserMessageParam(role="user", content=prompt)
+        return OpenAIUserMessageParam(content=prompt)
 
-    def build_prompt(self, messages: list[Message]) -> str:
+    def build_prompt(self, messages: list[OpenAIMessageParam]) -> str:
         categories = self.get_safety_categories()
         categories_str = "\n".join(categories)
         conversations_str = "\n\n".join(
@@ -377,7 +376,7 @@ class LlamaGuardShield:
 
         raise ValueError(f"Unexpected response: {response}")
 
-    async def run_moderation(self, messages: list[Message]) -> ModerationObject:
+    async def run_moderation(self, messages: list[OpenAIMessageParam]) -> ModerationObject:
         if not messages:
             return self.create_moderation_object(self.model)
 
@@ -388,6 +387,7 @@ class LlamaGuardShield:
             model=self.model,
             messages=[shield_input_message],
             stream=False,
+            temperature=0.0,  # default is 1, which is too high for safety
         )
         response = await self.inference_api.openai_chat_completion(params)
         content = response.choices[0].message.content