Suggestion to add support for dependency injection's IHttpClientFactory.

[AhmedZaki99]

When this library is used by applications with dependency injection configured, HttpClients should be created with the IHttpClientFactory. But our TodoistRestClient keeps creating new instances of HttpClient every time it is instantiated, which is not recommended.

I suggest then we add the option to use IHttpClientFactory when it's available by making the following changes:

1. Add a constructor overload for TodoistRestClient that takes an HttpClient instance as an argument:

public TodoistRestClient(string token, HttpClient httpClient)
{
    _httpClient = httpClient;

    _httpClient.BaseAddress = new Uri("https://api.todoist.com/sync/v9/");
    if (!string.IsNullOrEmpty(token))
    {
        _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
    }
}

2. Create an ITodoistClientFactory interface and TodoistClientFactory implementation to inject into the DI container, and use the provided IHttpClientFactory:

public interface ITodoistClientFactory
{
    TodoistClient CreateClient(string token);
}

internal sealed class TodoistClientFactory : ITodoistClientFactory
{
    private readonly IHttpClientFactory _httpClientFactory;

    public TodoistClientFactory(IHttpClientFactory httpClientFactory)
    {
        _httpClientFactory = httpClientFactory;
    }

    public TodoistClient CreateClient(string token)
    {
        var httpClient = _httpClientFactory.CreateClient();
        var todoistRestClient = new TodoistRestClient(token, httpClient);

        return new TodoistClient(todoistRestClient);
    }
}

3. Add an extension method to inject both the ITodoistClientFactory and IHttpClientFactory:

public static class TodoistServiceCollectionExtensions
{
    public static IServiceCollection AddTodoistClient(this IServiceCollection services)
    {
        services.AddHttpClient();
        services.AddSingleton<ITodoistClientFactory, TodoistClientFactory>();

        return services;
    }
}

That way, our TodoistClient can be instantiated the same way as HttpClient, using the factory pattern.

Usage:

• Service configuration (e.g. program.cs):

var builder = WebApplication.CreateBuilder(args);

builder.Service.AddTodoistClient();

• In other services (e.g. asp.net core controllers):

public class ExampleController : Controller
{
    private readonly ITodoistClientFactory _todoistClientFactory;

    public ExampleController(ITodoistClientFactory todoistClientFactory)
    {
        _todoistClientFactory = todoistClientFactory;
    }

    public IActionResult ExampleAction()
    {
        ITodoistClient client = _todoistClientFactory.CreateClient("API token");

        // Use the client to interact with the Todoist API.
        //...
    }
}