Implement Rate-limiter for Demo API

[godwinpinto]

Feature
Rate-limiter should be implemented for Demo API application

Solution
We can implement Bucket4J as a handler and attach to routers that will limit rate based on URL and IP address. This implementation could be tightly coupled with our application since the demo will be used as a showcase on internet and not for production. In production for core-api, one could choose their own implementation which come along with load balancers / api gateways / cloud providers without tightly coupling with the core system.

Reference
This is an implementation of spring Bucket4J: https://codersite.dev/rate-limit/ . The solution can be easily ported for vertx compliance