[API Proposal]: Add DI / ASP.NET Core integration (AddMocklyHandler, WebApplicationFactory support)

[dennisdoomen]

Motivation

Today HttpMock can only hand a client out: GetClient(), GetClientFactory() and GetMessageHandler(). There is no supported way to push the mock into an existing DI container.

That makes the most common integration-test scenario awkward. If the system under test resolves a typed client through IHttpClientFactory, or lives behind a WebApplicationFactory, you have to hand-roll handler replacement yourself.

Proposed API

A separate package (e.g. Mockly.Extensions.Http) so the core package stays dependency-free and net472-friendly:

// Replace the primary handler of a single named or typed client
services.AddHttpClient<IGitHubClient, GitHubClient>().AddMocklyHandler(mock);
services.AddHttpClient("github").AddMocklyHandler(mock);

// Replace the primary handler of every registered client
services.AddMockly(mock);

// ASP.NET Core integration tests
var factory = new WebApplicationFactory<Program>().WithMockly(mock);

Notes

• Should keep any DelegatingHandlers registered by the application in place, so resilience/retry pipelines (Microsoft.Extensions.Http.Resilience, Polly) are still exercised. Only the primary handler is swapped.
• Needs to work with both typed and named clients.
• Belongs in a separate package: it takes a dependency on Microsoft.Extensions.Http (and optionally Microsoft.AspNetCore.Mvc.Testing), neither of which should leak into the core package.