feat: implement GetMessageBatchResultsAsync method

src/AnthropicClient/Models/MessageBatchResult.cs

@@ -0,0 +1,26 @@
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a message batch result.
+/// </summary>
+public abstract class MessageBatchResult
+{
+  /// <summary>
+  /// Gets the type of the message batch result.
+  /// </summary>
+  public string Type { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="MessageBatchResult"/> class.
+  /// </summary>
+  /// <param name="type">The type of the message batch result.</param>
+  /// <returns>An instance of the <see cref="MessageBatchResult"/> class.</returns>
+  public MessageBatchResult(string type)
+  {
+    ArgumentValidator.ThrowIfNullOrWhitespace(type, nameof(type));
+
+    Type = type;
+  }
+}