fix: accept 204 No Content status code in ping method

[Mahoo12138]

Fix: Accept 204 status code for OPTIONS request in ping method

Description

Currently, the ping() method only accepts HTTP status code 200 for OPTIONS requests. However, according to HTTP/1.1 specification, status code 204 (No Content) is also a valid response for OPTIONS requests. This change makes the client more compatible with standard-compliant WebDAV servers.

Changes

• Modified ping() method to accept both 200 and 204 status codes
• Added documentation comment explaining the accepted status codes

Code Changes

/// Test whether the service can connect
/// Accepts both 200 OK and 204 No Content status codes as valid responses
Future<void> ping([CancelToken? cancelToken]) async {
  var resp = await c.wdOptions(this, '/', cancelToken: cancelToken);
  if (resp.statusCode != 200 && resp.statusCode != 204) {
    throw newResponseError(resp);
  }
}

Why

• HTTP/1.1 specification allows both 200 and 204 status codes for OPTIONS requests
• Some WebDAV servers (like Nginx) correctly return 204 for OPTIONS requests
• Current implementation unnecessarily restricts compatibility with standard-compliant servers

Testing

• Tested with Nginx WebDAV server (returns 204)
• Tested with other WebDAV servers (returns 200)
• Both cases now work correctly