Adding DI for Mocks and refactor into packages

  - An Interface has been created for managing the Service to manage People.
  - This interface allows to inject different implementation on the future.
  - We have created a Mock implementation and binded the Service to work with the Mock.
  - The test class is using DI for managing the controller (PeopleManager).
  - Now the controller is for comunicating with the PeopleService.
  - The Controller and Service are Singleton, we just need an instance of each
    during the application lifecycle. If we create an instance each time we want to perform an
    operation it could cause a memory leak.
  - Refactoring test after.