readAll method
Reads and returns all key-value pairs from storage.
Only string values are included. Keys with non-string values are ignored.
Implementation
@override
Future<Map<String, String>> readAll() async {
final keys = await _prefs.getKeys();
final result = <String, String>{};
for (final k in keys) {
final v = await _prefs.getString(k);
if (v != null) result[k] = v;
}
return result;
}