feat: create chat message

tests/AnthropicClient.Tests/EndToEnd/ClientTests.cs

@@ -0,0 +1,21 @@
+namespace AnthropicClient.Tests.EndToEnd;
+
+public class ClientTests(
+  HttpClientFixture httpClientFixture,
+  ConfigurationFixture configFixture
+) : EndToEndTest(httpClientFixture, configFixture)
+{
+  [Fact]
+  public async Task CreateChatMessage_WhenCalled_ShouldReturnChatResponse()
+  {
+    var request = new ChatMessageRequest(
+      model: AnthropicModels.Claude3Haiku,
+      messages: [new(MessageRole.User, [new TextContent("Hello!")])]
+    );
+
+    var result = await _client.CreateChatMessageAsync(request);
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().BeOfType<ChatResponse>();
+  }
+}