[notifications] User should be notified when background polling stops working

[Alberto Mardegan]

In Ubuntu there are some background processes which use Online Accounts to connect to remote services and check if there are new notifications for the user. Currently, account-polld does this for GMail and Twitter, and other use-cases might popup later (especially when we integrate chat services into messaging-app).

The problem
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Authentication tokens cached in Online Accounts do expire, or can become invalid at any time (because the user changes his password on the server, for example). When that happens, it's not always possible for a background process to retrieve a new authentication token: sometimes the remote server requests some interaction with the user (typically for re-entering username and password, or to renew the permission for the app), and this task can be completed only by a process capable of displaying some UI.

In order not to disrupt the user experience, we opted (bug #1401859) not to display a snap decision when such a situation arises, but now the user will never know if he's not receiving notifications because there are simply no notifications to be displayed, or because the polling has stopped because of an account error.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Renato Araujo Oliveira Filho (renatofilho)]

The same is valid for contact/calendar/file/e-mail/etc..

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Renato Araujo Oliveira Filho (renatofilho)]

Online account settings page does not show any indication of that the account token is invalid. The opposite from Desktop online-account page where you see a indication that the account authentication has been revoked and you need to re-authenticate it.