isSuccess

Checks whether the asynchronous operation completed successfully.

This method determines success by checking if the exception field is null. A null exception indicates that the operation completed without errors.

Usage pattern: Always call this method first before accessing getData or getException to determine which accessor to use. Example:

	  if (result.isSuccess()) {
	      // Operation succeeded - safe to get data
	      String token = result.getData().getToken();
	  } else {
	      // Operation failed - safe to get exception
	      Exception error = result.getException();
	      Log.e("App", "Error: " + error.getMessage());
	  }