We use this callback to feed candidates to ice4j user applications that
support trickle ICE. The interface provides two methods that allow passing
candidates to applications either one-by-one or in batches. The former would
typically be used for harvesters such as STUN, where candidates are learned
one per message. Discovering batches of candidates is possible when querying
a TURN server, which in many cases would return both server reflexive (STUN)
and relayed (TURN) candidates.