Add option for redirect override in authenticate call

[danielcorin]

No description provided.

[jaredhanson]

Can you describe the use case here? How would the override operate in a way different than the standard redirect?

[coveralls]

Coverage remained the same at 100.0% when pulling 733cbed on danielcorin:dc/auth-redirect-option into 1ac8cbb on jaredhanson:master.

[danielcorin]

We're seeking to expose the status variable configuration which exists in the core passport library here but is no longer exposed in this library. I believe this change would preserve the passport library's original behavior described in the comment.

Redirect to `url` with optional `status`, defaulting to 302.

Our use case is that we'd like to use passport and passport-oauth2 to construct the URL of our external authentication server and return it as a Location header, but don't actually want it to instruct the browser to redirect.

[jaredhanson]

My suggestion would be to add a statusCode option, something like:

passport.authenticate({ statusCode: 303});

Seems more readable that passing a function that takes the strategy itself as an argument. And I can't think of any use cases where something other than the status code would be changed on redirect.

[danielcorin]

That sounds reasonable to me. Let me author a new PR and I will close this one out once I do. Thanks for the feedback!

[danielcorin]

Closing in favor of #123