Rate Limiter Implementation

You are required to design and implement a rate limiter for an API service. The rate limiter should ensure that a single client (or user) does not exceed a predefined number of requests within a specified time window. The following are the key requirements:

1. Create a class (or module) that provides a function/method, for example, allowRequest(userId, timestamp), which returns a boolean value indicating whether the request should be allowed.

2. Each user is allowed a maximum of N requests within a moving time window of T seconds. The specific numbers (N and T) can be defined in your implementation, but they should be configurable.

3. Your implementation should efficiently handle a large number of users and incoming requests.

4. Consider the implications of concurrent requests and ensure that your solution is thread-safe if your chosen programming language requires you to handle concurrency explicitly.

5. Write tests or provide sample code demonstrating that your rate limiter works as expected under different scenarios (for example, users hitting the limit, users with intermittent requests, etc.).

6. Bonus: Extend your solution to support multiple rate-limiting rules (e.g., different limits for different API endpoints or user roles).

Provide a complete implementation along with any necessary documentation or comments explaining your approach.