1.14. Check whether an entity is active
Fast DDS Statistics Backend keeps the statistical data record of
all the entities that have at some point been detected by a monitor.
However, it is possible that some of this entities have already abandoned the network, thus becoming inactive.
For this reason, StatisticsBackend exposes a is_active() function that returns whether an entity is active,
given its EntityId.
bool active = StatisticsBackend::is_active(entity_id);