CallbackInterceptor class

A simple interceptor that can be created with function callbacks

This is useful for creating quick interceptors without having to create a full class that extends FittorInterceptor.

Example:

final loggingInterceptor = CallbackInterceptor(
  onRequest: (request) async {
    print('Sending request to ${request.url}');
    return request;
  },
  onResponse: (response) async {
    print('Received response: ${response.statusCode}');
    return response;
  },
);