Locale not correct on social login

[giorgio93p]

In fact, this issue has two different cases

1. Account creation on social login: locale id is not set correctly, it's always the default one. We can easily fix this by overriding allauth's social account adapter (see commit a306b1d).
2. Social login with existing account: locale cookie is never written (because execution does not pass from our login view for normal logins), so the locale shown after login is the one that it was before login, instead of the one saved in user profile. Since we need a response on which to set the cookie and since each social provider has different urls and views, this can't be fixed equally easily.

[adamhooper]

Urgh. It looks like we'll need the allauth.account.signals.user_logged_in

in allauth.account.utils.perform_login():

    try:
        adapter.login(request, user)
        response = HttpResponseRedirect(
            get_login_redirect_url(request, redirect_url))

        if signal_kwargs is None:
            signal_kwargs = {}
        signals.user_logged_in.send(sender=user.__class__,
                                    request=request,
                                    response=response,
                                    user=user,
                                    **signal_kwargs)
        adapter.add_message(
            request,
            messages.SUCCESS,
            'account/messages/logged_in.txt',
            {'user': user})
    except ImmediateHttpResponse as e:
        response = e.response
    return response

The adapter can't add a cookie to the response. (Except in add_message(), but that's waaaaay too janky.)

So we're forced to modify the response's cookies in a signal handler. Frustrating! But that seems to be our only recourse.

[giorgio93p]

We could also override the urls and views of the specific providers we want to be able to use. Not general, but avoids signals.

[adamhooper]

That's too much work. Signals are the least-janky way.