public class RateLimitDecorator : IApi
{
    private readonly IApi _inner;
    private readonly TokenBucket _bucket;
    public RateLimitDecorator(IApi a, int m) => (_inner, _bucket) = (a, new TokenBucket(m));
    public Response Call(string ep)
        => _bucket.Take() ? _inner.Call(ep) : Response.TooManyRequests();
}