LinkDecorator.cs

internal class LinkDecorator : IRenderable
{
    private readonly IRenderable _inner;
    private readonly string _url;
    public LinkDecorator(IRenderable inner, string url)
    {
        _inner = inner;
        _url = url;
    }

    public string Render() => $"<a href=\"{_url}\">{_inner.Render()}</a>";
}