post https://api.olxgroup.com/oauth/v1/token
"grant_type": "refresh_token"
A refresh_token is a unique token to obtain a new access_token without authorizing the user again.
The refresh_token is valid for one year, and the access_token is valid for one hour.
The response depends on the state of access_token:
access_token is expired; you will receive a new access_token in the response.
access_token is not expired yet; you will receive a new access_token in the response.
access_token is invalid, you will receive an error message, and the user needs to authorize again to get a new token;
Store access_token and refresh_token and keep them in a safe place.