feat: create chat message

src/AnthropicClient/Utils/ArgumentValidator.cs

@@ -0,0 +1,23 @@
+namespace AnthropicClient.Utils;
+
+/// <summary>
+/// Provides methods to validate arguments.
+/// </summary>
+public static class ArgumentValidator
+{
+  /// <summary>
+  /// Throws an <see cref="ArgumentNullException"/> if the value is null.
+  /// </summary>
+  /// <typeparam name="T">The type of the value.</typeparam>
+  /// <param name="value">The value to check.</param>
+  /// <param name="name">The name of the value.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the value is null.</exception>
+  /// <returns>Nothing.</returns>
+  public static void ThrowIfNull<T>(T? value, string name)
+  {
+    if (value is null)
+    {
+      throw new ArgumentNullException(name);
+    }
+  }
+}