[Feature] API Routes for employees

[ernestoresende]

Umbrella issue for all employee routes

We should have routes for creating, listing and updating employees entities.

• POST /employee route to create a new employee #38
• GET /employee/:employee_id route to create a new employee #39
• PUT /employee/:employee_id route to update information on a employee #40
• DELETE /employee/:employee_id route to deactivate an employee #41