Push notifications via TwinPush (for Appcrue)

Enable Moodle to send messages through the notification service of AppCrue application using TwinPush API.
AppCRUENotify message output
Enables Moodle to send messages using TwinPush API. It was developed  for the notification service of AppCrue mobile application).
What is AppCRUE?
AppCRUE ( https://tic.crue.org/appcrue/ ) is a mobile App develop by the CRUE (Conference of Rectors of Spanish Universities) and Santander Bank. It is used by 44 spanish universities and more than 150 000 students.
What is TwinPush?
AppCRUE uses as notification platform TwinPush ( https://twinpush.com/ ). TwinPush is a Marketing Mobile Platform that allows sending Push notifications to Smartphones. It offers Android SDK, IOS SDK, REST API.
This plugin can be used for any other application using TwinPush or a similar REST API.
For developing with TwinPush API
TwinPush provides a site with resources for developers: https://developers.twinpush.com/developers .
This plugin uses the API explained on https://developers.twinpush.com/developers/api . In particular, it is very helpful to follow the [ Common error messages ]( https://developers.twinpush.com/developers/api#common-error-messages ) to help you understand the source of the traced errors.
Functionality
This message output plugin provides the following services:
– Allow admins to send only messages from the “News” forum of the course.
– Format the messages from the forum, instant messaging to fit better in the mobile notifications.
– Select which field in the user’s profile is used to match the user in TwinPush platform.
– Sends every message that pass the former conditions to the recipient via TwinPush.
– Can add messages (with same subject, body, url) to a buffer allowing to send them to multiple users in a single request.
The notifications can be enabled/disabled/forced using Moodle’s core notifications settings and user’s preferences.
Known issues