mayReceive method
Whether principalId may receive event (04 7.2, 05 6): a personal event only its
audience, a channel event those who see the channel, a space event those who see a
channel of the space, an instance event everyone.
Implementation
bool mayReceive(String principalId, FakeEvent event) {
if (event.audience != null) return event.audience == principalId;
final channel = event.scope['channel_id'] as String?;
if (channel != null) return seesChannel(principalId, channel);
final space = event.scope['space_id'] as String?;
if (space != null) return seesSpace(principalId, space);
return true;
}