BACtrackStatus objects are emitted on the FlutterBactrack.statusStream. Not all
states have an associated message. In these cases the message string is empty,
it will never be null.
This class provides the main interface to the BACtrack Flutter plugin. It is
a singleton so only one instance will ever be created in a Flutter application.
There is one corresponding BACtrackState for each of the methods in the BACtrackAPICallbacks
object defined in the BACtrack SDK. These states are named the same as the callback methods
minus the BACtrack prefix on each. The only exceptions are: