Add, update, and delete quizzes

The first thing we'll do is to implement the add, update, and delete methods for our Web API's QuizController. We'll adhere to RESTful conventions and good practices, using the proper HTTP verb for each scenario: POST to create, PUT to update, and DELETE to delete.

Updating QuizController

Remember the #region RESTful conventions methods in our QuizController.cs file? It's time to update its contents to support CRUD operations on Quiz entities.

Here's the new code (new and updated lines are highlighted):

[...]

#region RESTful conventions methods
/// <summary>
/// GET: api/quiz/{id}
/// Retrieves the Quiz with the given {id}
/// </summary>
/// <param name="id">The ID of an existing Quiz</param>
/// <returns>the Quiz with the given {id}</returns>
[HttpGet("{id}")]
public IActionResult Get(int id)
{
    var quiz = DbContext.Quizzes.Where(i => i.Id == id)
        .FirstOrDefault();

    // handle requests asking for non-existing...