write method
Writes payload to the cache namespace and key.
Implementation
void write(String cacheDir, String namespace, String key, String payload) {
final String dir = p.join(cacheDir, namespace);
_fs.createDirectory(dir);
final String path = p.join(dir, '$key.json');
_fs.writeFile(
path,
jsonEncode(
<String, Object?>{
'storedAt': DateTime.now().toIso8601String(),
'payload': payload,
},
),
);
}