use DefaultAzureCredential instead of AzureCliCredential (#3860)

dotnet/samples/GettingStarted/AgentOpenTelemetry/Program.cs

@@ -110,7 +110,10 @@ static async Task<string> GetWeatherAsync([Description("The location to get the
     return $"The weather in {location} is cloudy with a high of 15°C.";
 }
 
-using var instrumentedChatClient = new AzureOpenAIClient(new Uri(endpoint), new AzureCliCredential())
+// WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
+// In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
+// latency issues, unintended credential probing, and potential security risks from fallback mechanisms.
+using var instrumentedChatClient = new AzureOpenAIClient(new Uri(endpoint), new DefaultAzureCredential())
     .GetChatClient(deploymentName)
         .AsIChatClient() // Converts a native OpenAI SDK ChatClient into a Microsoft.Extensions.AI.IChatClient
         .AsBuilder()