subscribe method
Subscribe a new query set. Returns the assigned querySetId.
Awaits the matching SubscribeApplied so initial rows are in the cache.
Resolves without throwing if the manager is disposed, the connection
drops, or the server rejects the subscription before then.
Implementation
Future<int> subscribe(List<String> queries) async {
final querySetId = _nextQuerySetId++;
_subscriptionsByQuerySetId[querySetId] = List.of(queries);
await _sendSubscribeAndWait(
querySetId,
_subscriptionsByQuerySetId[querySetId]!,
);
return querySetId;
}