So far, realmd was being merely used to auto-discover a list of realms,
and validate whether the user entered a valid realm or not before
prompting for credentials. This sounds nice in theory but, in
practice, it is far too fragile. For example, realmd gets frequently
tripped up by Fedora's Kerberos setup which uses _kerberos._tcp
instead of the more common _kerberos._udp SRV record. Secondly, the
realm validation isn't snappy and can take a while, so the user has to
wait a bit before she is able to enter her credentials.

The current UI is also odd because it presents separate fields for
entering the realm and the username. Most people are used to entering
username@realm or username@REALM because of their familiarity with
email addresses and kinit.

Therefore, the account addition UI has now been re-written without
realmd. There is only one field for the user to enter her principal,
and the realm is automatically capitalized if it isn't. It entirely
relies on libkrb5.so to validate the principal during the initial
sign-in once the credentials have been entered.

https://bugzilla.gnome.org/show_bug.cgi?id=789187

https://bugzilla.gnome.org/show_bug.cgi?id=789187

GMail supports both STARTTLS and non-STARTTLS for SMTP:
https://support.google.com/mail/answer/7126229?hl=en
https://support.google.com/a/answer/176600?hl=en
https://www.lifewire.com/what-are-the-gmail-smtp-settings-1170854

https://bugzilla.gnome.org/show_bug.cgi?id=772305

... via the OAuth1 web page.

Ever since Flickr was added, clicking the "NO, THANKS" widget in the
web page has redirected to https://www.gnome.org/, which is specified
as GNOME's website in Flickr's App Garden, instead of to the specified
callback URI and/or returning an error. The click on this element
cannot be intercepted because the "click" event handler is not being
called (WebKit bug?). Current attempts to inspect that element breaks
the WebKit inspector.

Instead, let's also use https://www.gnome.org/ as the callback URI,
and use the lack of a query when redirecting to it to close the window.
It might need adjustments when there is a different OAuth1-based
provider.

This keeps the code in sync with GoaOAuth2Provider.

... instead of the user's Flickr home page.

Changing the OAuth endpoints to the documented www.flickr.com, instead
of m.flickr.com, fixes the problem. Both present the same compact UI,
so there is no need to explicitly ask for the mobile version of it.

This reverts commit 219b3d72

https://bugzilla.gnome.org/show_bug.cgi?id=786007

With WebKit1, the Accept-Language header could be set for every
request based on g_get_language_names by using the SoupSession's
accept-language-auto property. This was lost during the port to
WebKit2.

Since WebKit2 doesn't expose its internal SoupSession, the same
functionality is now implemented using g_get_language_names and
webkit_web_context_set_preferred_languages.

Fallout from 81434a02

https://bugzilla.gnome.org/show_bug.cgi?id=758716

Mention the Graph API Explorer. It is a handy tool for debugging issues
with the wire protocol.

https://bugzilla.gnome.org/show_bug.cgi?id=785726

Ever since version 2.3 of the Graph API was retired on 8th July, it
stopped including "email" in the JSON when a GET request is issued
against https://graph.facebook.com/me?access_token=...

Now it needs to be explicitly asked for. The changelog [1] for version
2.4 says:
  "To try to improve performance on mobile networks, Nodes and Edges
   in v2.4 requires that you explicitly request the field(s) you need
   for your GET requests. For example, GET /v2.4/me/feed no longer
   includes likes and comments by default, but GET
   /v2.4/me/feed?fields=comments,likes will return the data."

It seems that "id" is always included, but we mention it anyway.

The "username" fallback that was added in commit 10c77f17 has
been removed because requesting it leads to:
  {
    "error": {
      "message": "(#12) username field is deprecated for versions v2.0
                  and higher",
      "type": "OAuthException",
      "code": 12,
      "fbtrace_id": "AJYNXiIv00W"
    }
  }

We will have to investigate whether we need a new fallback for the
presentation identity.

[1] https://developers.facebook.com/docs/apps/changelog

https://bugzilla.gnome.org/show_bug.cgi?id=785726

The json_object_get_string_member API expects the member to be present.
Therefore, we should not use its return value to determine its
availability. Otherwise it will lead to:
  Json-CRITICAL **: json_object_get_string_member: assertion
    'node != NULL' failed

https://bugzilla.gnome.org/show_bug.cgi?id=785726

The log domain for this piece of code is "GoaBackend", not "goa". Use
the standard G_LOG_DOMAIN macro, which is already defined, to specify
the log domain.

Adds a missing chain-up in constructed, drops Facebook XMPP and adds
skypeweb.

To ensure the translation data are loaded from the correct prefix even
if libintl and gnome-online-accounts are installed in different
prefixes, we must call bindtextdomain and bind_textdomain_codeset
before translating messages.

To keep the code clean, gconstructor.h from GLib is copied to support
running code when the library is loaded, so we can have a constructor
to call gettext functions.

https://bugzilla.gnome.org/show_bug.cgi?id=760440

Google recently updated their web authentication UI. The ID and name
of the identity node has changed.

Signed-off-by: Trần Ngọc Quân <vnwildman@gmail.com>