register method
void
register()
Registers a service provider.
service is a name string (e.g. 'location', 'prefs').
handler receives the method name and parameters, and returns
the result.
Implementation
void register(
String service,
FutureOr<Object?> Function(
String method,
Map<String, dynamic> params,
) handler,
) {
_services[service] = handler;
}