refresh method
Fetches the session list from the node.
Implementation
Future<void> refresh() async {
final prev = state.value.data;
state.value = AsyncState.loading(data: prev, stale: prev != null);
try {
final sessions = await _service.listSessions(nodeId);
state.value = AsyncState.ready(sessions);
} on AppError catch (e) {
state.value = AsyncState.error(e, data: prev);
}
}