Add ResponseImageInput test for OpenAI image handling

Introduces a new test method `ResponseImageInput` in `ResponsesTests.cs`. This method verifies the functionality of sending an image and text prompt to the OpenAI API. It checks the response for output items and logs the input items asynchronously, enhancing the test coverage for image input handling.

Author: waltervvb

sdk/openai/Azure.AI.OpenAI/tests/ResponsesTests.cs

@@ -90,6 +90,38 @@ public async Task FileSearch(string deploymentName)
         }
     }
 
+    [RecordedTest]
+    [TestCase(Gpt4oMiniDeployment)]
+    public async Task ResponseImageInput(string deploymentName)
+    {
+        OpenAIClient topLevelClient = GetTestTopLevelClient(DefaultResponsesConfig);
+        OpenAIFileClient fileClient = topLevelClient.GetOpenAIFileClient();
+        VectorStoreClient vectorStoreClient = topLevelClient.GetVectorStoreClient();
+        OpenAIResponseClient client = topLevelClient.GetOpenAIResponseClient(deploymentName);
+
+        Uri imageUri = new("https://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Microsoft_logo.svg/512px-Microsoft_logo.svg.png");
+        ResponseContentPart imagePart = ResponseContentPart.CreateInputImagePart(imageUri);
+        ResponseContentPart textPart = ResponseContentPart.CreateInputTextPart("Describe this image");
+
+        List<ResponseContentPart> contentParts = [imagePart, textPart];
+
+        OpenAIResponse response = client.CreateResponse(
+                    inputItems:
+                    [
+                        ResponseItem.CreateSystemMessageItem("You are a helpful assistant that describes images"),
+                        ResponseItem.CreateUserMessageItem(contentParts)
+                    ]);
+
+        Assert.That(response.OutputItems?.Count, Is.EqualTo(1));
+        MessageResponseItem? message = response?.OutputItems?[0] as MessageResponseItem;
+        Assert.That(message, Is.Not.Null);
+
+        await foreach (ResponseItem inputItem in client.GetResponseInputItemsAsync(response?.Id))
+        {
+            Console.WriteLine(ModelReaderWriter.Write(inputItem).ToString());
+        }
+    }
+
     [RecordedTest]
     public async Task ComputerToolWithScreenshotRoundTrip()
     {