Refactor agent client handling and improve error checks

Introduces a get_chat_client method to MCPEnabledBase for consistent agent client retrieval and updates agent initialization in FoundryAgentTemplate and ReasoningAgentTemplate to use it. Enhances error handling and validation in API router endpoints, including improved user and team configuration checks, and updates RAI validation calls to support additional parameters.

Author: Fr4nc3

src/backend/v4/magentic_agents/common/lifecycle.py

@@ -135,6 +135,19 @@ async def _after_open(self) -> None:
         """Subclasses must build self._agent here."""
         raise NotImplementedError
 
+    def get_chat_client(self, chat_client) -> AzureAIAgentClient:
+        """Return the underlying ChatClientProtocol (AzureAIAgentClient)."""
+        if chat_client:
+            return chat_client
+        if self._agent:
+            return self._agent.chat_client  # type: ignore
+        chat_client = AzureAIAgentClient(
+                        project_endpoint=self.project_endpoint,
+                        model_deployment_name=self.model_deployment_name,
+                        async_credential=self.creds,
+                    )
+        return chat_client
+    
     async def get_database_team_agent(self) -> Optional[AzureAIAgentClient]:
         """Retrieve existing team agent from database, if any."""
         chat_client = None

src/backend/v4/magentic_agents/foundry_agent.py

@@ -248,7 +248,7 @@ async def _after_open(self) -> None:
                 self.logger.info("Initializing agent in MCP mode.")
                 tools = await self._collect_tools()
                 self._agent = ChatAgent(
-                    chat_client=chatClient or self.client,
+                    chat_client=self.get_chat_client(chatClient),
                     instructions=self.agent_instructions,
                     name=self.agent_name,
                     description=self.agent_description,

src/backend/v4/magentic_agents/reasoning_agent.py

@@ -110,7 +110,7 @@ async def _after_open(self) -> None:
             chatClient = await self.get_database_team_agent()
 
             self._agent = ChatAgent(
-                chat_client = chatClient or self.client,
+                chat_client = self.get_chat_client(chatClient),
                 instructions=self.agent_instructions,
                 name=self.agent_name,
                 description=self.agent_description,