Feature

Error callbacks allow the host applications to be notified when the SDK encounters unexpected errors.

Closes #315

How to test

1. Clone the its-client project on your IDE.
2. Ensure that you have Gradle to be able to build the java/iot3 modules (core, mobility and examples).
3. Find the Iot3CoreExample and Iot3MobilityExample classes in the examples module.
4. Run them without changing the placeholder parameters.

Expected results:

On the console, you should see the following for Iot3CoreExample:

IoT3Core error: java.net.UnknownHostException: mqtt_host: Temporary failure in name resolution

And the following for Iot3MobilityExample:

IoT3Mobility error: java.net.UnknownHostException: mqtt_host: Temporary failure in name resolution
IoT3Mobility error: MQTT client is not connected.
...
IoT3Mobility error: MQTT client is not connected.