Implement a random fixed-size load balancer

## Problem: Build a simple load balancer Implement a minimal in-memory load balancer that routes each incoming request to **one backend node chosen uniformly at random**. ### Requirements - The load balancer maintains a **set of backend nodes** (e.g., strings or IDs). - The number of nodes is bounded by a fixed maximum capacity `K`. - Support these operations: 1. `addNode(nodeId)` - Adds a node if it is not already present. - If the load balancer is at capacity `K`, define and document what happens (e.g., reject the add / throw). 2. `removeNode(nodeId)` - Removes the node if present; otherwise no-op. 3. `route()` (or `getNodeForRequest()`) - Returns a node chosen **uniformly at random** from the currently active nodes. - If there are **no nodes**, define and document what happens (e.g., return null / throw). ### Constraints / Edge cases to handle - Adding duplicates. - Removing a non-existent node. - Routing when empty. - Keeping `route()` efficient (ideally O(1)). ### Deliverable Describe the data structures and implement the API (language-agnostic or Java-style).