serialize method
Serializes the Request instance into a Nostr message format.
The Nostr message format is a JSON-encoded array with the following structure:
"REQ", subscription_id, filter JSON, filter JSON, ...
Implementation
String serialize() {
final theFilters =
json.encode(filters.map((item) => item.toJson()).toList());
final header = json.encode(['REQ', subscriptionId]);
return '${header.substring(0, header.length - 1)},${theFilters.substring(1, theFilters.length)}';
}