Fake login on dev

[g105b]

It's really useful to be able to make a quick login while on development, but it doesn't necessarily need to perform the whole authentication on a remote provider.

It would be useful to be able to perform a fake login that only works on localhost by default.

[g105b]

function example(Authenticator $auth, Uri $uri):void {
	if(!$auth->isLoggedIn() && $uri->getHost() === "localhost") {
		$auth->fakeLogin("the-user-id-to-use");
	}
}

The fakeLogin function would redirect back, as if it were coming from the provider, with a pre-authenticated user of the provided ID.

[g105b]

Needs unit testing before this can be closed.