Auth 2.0 Cleanup: Revisit cleanup events/context

[HaoK]

Sharing context for core IAuthenticationHandler and the events might be a bit awkward, also see if there's any improvements that can be made for the events as a whole

[kevinchalet]

@HaoK now that the authentication scheme is not longer stored in the options, retrieving it from the events is next to impossible. What do you think of introducing a Scheme property in BaseContext?

public class BaseContext
{
    protected BaseContext(HttpContext context, string scheme);

    public string Scheme { get; }
}

If BaseContext was moved to this repo, we could even expose it as a strongly typed property:

public class BaseContext
{
    protected BaseContext(HttpContext context, AuthenticationScheme scheme);

    public AuthenticationScheme Scheme { get; }
}

[kevinchalet]

@HaoK another question: do you remember why you've decided to rename BaseControlContext.SkipToNextMiddleware() to Skip()? The new name is not as clear as the old one, and doesn't really reflect what happens in practice.

[HaoK]

For events, we have: #1181 to revisit exactly that question.

The whole Skip/Handled thing is a bit weird, and what makes sense in some uses (SkipToNextMiddleware) makes sense when its being run in the HandleRequest of a callback for an auth request, but doesn't make sense anywhere else. We can use the same events issue to track revisiting that as well.

[kevinchalet]

For events, we have: #1181 to revisit exactly that question.

So this is the right place?

The whole Skip/Handled thing is a bit weird.

Weird... but insanely powerful 😅

What makes sense in some uses (SkipToNextMiddleware) makes sense when its being run in the HandleRequest of a callback for an auth request, but doesn't make sense anywhere else.

Sure, but doesn't the BaseControlContext name imply that the event should be used only where we have flow control (i.e from HandleRequestAsync) and where Skip really means "skip the default logic and invoke the rest of the pipeline"?

[HaoK]

Possibly, but I think we are using it in a variety events, not just ones that are invoked through the request processing pipeline.