feat: add models for streaming messages

tests/AnthropicClient.Tests/EndToEnd/ClientTests.cs

@@ -18,4 +18,24 @@ public class ClientTests(
     result.IsSuccess.Should().BeTrue();
     result.Value.Should().BeOfType<ChatResponse>();
   }
+
+  [Fact]
+  public async Task CreateChatMessage_WhenCalledWithStreamRequest_IteratesOverChatResponse()
+  {
+    var request = new StreamChatMessageRequest(
+      model: AnthropicModels.Claude3Haiku,
+      messages: [new(MessageRole.User, [new TextContent("Hello!")])]
+    );
+
+    var response = _client.CreateChatMessageAsync(request);
+    
+    var events = new List<AnthropicEvent>();
+
+    await foreach (var e in response)
+    {
+      events.Add(e);
+    }
+
+    events.Should().NotBeEmpty();
+  }
 }