Resync to upstream/master (fix segfault in webapp.d + return bool from login())

[wilzbach]

So the main problem turned out to be that I use a different method to check for the login state, which means that the session is never added to req.context. The failure manifested as nasty segfault due to Session being null. Thus, the second commit will add the session to req.context as fallback if settings are supplied to oauthSession. In theory, login should also have a check for this - maybe in userAuthUri?

The first commit allows to use the result of the login function, s.t. instead of

webapp.login(req, res, googleOAuthSettings, null, googleScopes))
if (!res.headerWritten)

We can write:

if (webapp.login(req, res, googleOAuthSettings, null, googleScopes))
{

}

[thaven]

I understand the inconvenience in situations where oauth is not being used to keep track of user logins. Seems sensible to reconsider the naming, and possibly usage, of isLoggedIn. This commit does not seem to solve the problem correctly.

[thaven]

The reason for oauthSession to not take a settings parameter, is that it should be possible for multi-provider apps to get the OAuthSession regardless of the settings used to login.

As mentioned in the documentation comment, oauthSession is just a getter to be used only after checking for session availability and validity.

[thaven]

Even with this, there's still the possibility of oauthSession returning null, i.e. when the user did not login with OAuth. So the need for a null-check will always exist, unless a session is known to be available (e.g. isLoggedIn is known to have returned true for this request).

[thaven]

This would introduce a serious bug. Should only return true if a session is available.

[thaven]

Added commit 88e11ac to master.