Design employee and company classes with tests

## Object-Oriented Design + Unit Testing You are implementing a small in-memory model for a company and its employees. The interviewer will give only input/output expectations, so you must clarify requirements and design clean APIs. ### Part 1 — Employee Design an `Employee` object with at least: - `id` (unique identifier) - `name` - `email` ### Part 2 — Company Design a `Company` object that manages many employees. Support operations such as: - Add an employee - Read/lookup an employee by `id` - Update an employee’s `email` by `id` - Delete/remove an employee by `id` ### Part 3 — Behavior and validation (clarify assumptions) Define and implement behavior for edge cases such as: - Adding an employee with a duplicate `id` - Looking up/updating/deleting an `id` that does not exist - Invalid emails (if you choose to validate) ### Part 4 — Testing requirement Write unit tests for each part/operation (the interview requires tests that can be executed successfully). Tests should cover: - Happy paths - Key edge cases and error handling ### Part 5 — Code quality expectations Aim for: - Clear method names and return values - Appropriate exceptions or error results - Maintainable structure (separation of concerns, minimal coupling)