feat: first take of adding caching support

src/AnthropicClient/Models/Content.cs

@@ -11,6 +11,12 @@ public abstract class Content
   /// Gets the type of the content.
   /// </summary>
   public string Type { get; init; } = string.Empty;
+  
+  /// <summary>
+  /// Gets the cache control to be used for the content.
+  /// </summary>
+  [JsonPropertyName("cache_control")]
+  public CacheControl? CacheControl { get; init; }
 
   [JsonConstructor]
   internal Content()
@@ -26,4 +32,16 @@ public abstract class Content
   {
     Type = type;
   }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="Content"/> class.
+  /// </summary>
+  /// <param name="type">The type of the content.</param>
+  /// <param name="cacheControl">The cache control to be used for the content.</param>
+  /// <returns>A new instance of the <see cref="Content"/> class.</returns>
+  protected Content(string type, CacheControl cacheControl)
+  {
+    Type = type;
+    CacheControl = cacheControl;
+  }
 }