The application's configuration

To make the application more flexible and easy to configure, we are going to create a configuration file. This way, we don't need to hardcode the URL and access keys; also, if we need to change these settings, changes in the source code will not be required.
We are going to create a config file in the YAML format to store information that will be used by our application to authenticate, make requests to the Spotify RESP API endpoints, and so on.