create method
Opens a writer for a new vault file at path. Supports writes at any offset as long as
every chunk is filled by exactly one sequential writer (true for download segments that
are aligned to UVaultHeader.chunkSize).
Implementation
Future<UVaultWriter> create(String path, {int chunkSize = defaultVaultChunkSize}) async {
final (UVaultHeader header, UAead aead) = await newFile(chunkSize: chunkSize);
final UStorageSink sink = await _backend.open(path, truncate: true);
await sink.writeAt(0, header.encode());
return UVaultWriter._(header, aead, sink);
}