Push Notifications (XEP-0357) implementation

Fixes SMACK-738

documentation/extensions/pushnotifications.md

@@ -0,0 +1,82 @@
+Push Notifications
+==================
+
+Allows to manage how XMPP servers deliver information for use in push notifications to mobile and other devices.
+
+  * Check push notifications support
+  * Enable push notifications
+  * Disable push notifications
+  * Remote disabling of push notifications
+
+
+**XEP related:** [XEP-0357](http://xmpp.org/extensions/xep-0357.html)
+
+
+Get push notifications manager
+------------------------------
+```
+PushNotificationsManager pushNotificationsManager = PushNotificationsManager.getInstanceFor(connection);
+```
+
+
+Check push notifications support
+--------------------------------
+
+```
+boolean isSupported = pushNotificationsManager.isSupportedByServer();
+```
+
+
+Enable push notifications
+-----------------------
+
+```
+pushNotificationsManager.enable(pushJid, node);
+```
+or
+```
+pushNotificationsManager.enable(pushJid, node, publishOptions);
+```
+*pushJid* is a `Jid`
+
+*node* is a `String`
+
+*publishOptions* is a `HashMap<String, String>` (which means [option name, value])
+
+
+Disable push notifications
+--------------------------
+
+```
+pushNotificationsManager.disable(pushJid, node);
+```
+*pushJid* is a `Jid`
+
+*node* is a `String`
+
+**Disable all**
+
+```
+pushNotificationsManager.disableAll(pushJid);
+```
+*pushJid* is a `Jid`
+
+
+Remote disabling of push notifications
+--------------------------------------
+
+```
+// check if the message is because remote disabling of push notifications
+if (message.hasExtension(PushNotificationsElements.RemoteDisablingExtension.ELEMENT, PushNotificationsElements.RemoteDisablingExtension.NAMESPACE)) {
+  
+  // Get the remote disabling extension
+ PushNotificationsElements.RemoteDisablingExtension remoteDisablingExtension = PushNotificationsElements.RemoteDisablingExtension.from(message);
+
+  // Get the user Jid
+  Jid userJid = remoteDisablingExtension.getUserJid();
+
+  // Get the node
+  String node = remoteDisablingExtension.getNode();
+
+}
+```