put method
Creates or updates a value. Returns true if created.
Implementation
Future<bool> put(String key, Uint8List data) async {
final r = await _send(opPut, key, data);
if (r.isDenied) throw WsDeniedException('PUT: ${utf8.decode(r.data)}');
if (r.isError) throw WsException('PUT: ${utf8.decode(r.data)}');
return r.isCreated;
}