OAuth2: Refresh the token without aborting the sync

[ogoffart]

OAuth2 access token typically only has a token valid for 1 hour.
Before this patch, when the token was timing out during the sync, the
sync was aborted, and the ConnectionValidator was then requesting a new
token, so the sync can be started over.
If the discovery takes longer than the oauth2 validity, this means that
the sync can never proceed, as it would be always restarted from scratch.

With this patch, we try to transparently renew the OAuth2 token and restart
the jobs that failed because the access token was invalid.

Note that some changes were required in the GETFile job because it handled
the error itself and so it was erroring the jobs before its too late.

Issue #6814

[ogoffart]

I have been testing this by adding this in HttpCredential::fetchFromKeychain

    auto timer = new QTimer(this);
    timer->setInterval(10000);
    QObject::connect(timer, &QTimer::timeout, this, [this] { qWarning() << "YOLO";  _password = "yolo"; });
    timer->start();

This simulate an expiration of the access token every 10 second. Then one
can verify that the sync goes through and that other side jobs such as expanding
the "choose what to sync" tree, are working correctly.

Making an automated test for this would be quite hard as this is in the HttpCredential class, and this class is currently not automatically tested/testable. (All our sync engine test are using fake credentials)

[ckamm]

This works because newReplyHook reconnects the signals, right? Suggestion:

// Redirects and auth failures (oauth token renew) will end up restarting the job. We do not want to process
// further data from the initial request. newReplyHook() will reestablish signal connections for the follow-up
// request.

Also, what if there's a 401 that doesn't cause a new job to be spawned? Then finishedSignal() wouldn't be emitted.

[ogoffart]

Right, I now changed GETFileJob::finished so this does not happen

[ckamm]

Alright, that looks like it works. What do you think about adding the comment?

[ogoffart]

Comment updated

[guruz]

@micbar Do you want to help us to test this in one the actual setups?

[micbar]

I could send a patched client to the user with the issue.

[ogoffart]

@micbar : I just merged the patch, which means that the 2.5.1 daily build from tomorrow will have the patch. They could try the daily build.

[guruz]

I could send a patched client to the user with the issue.

Would be great.