Refresh-Token: O que é e como funciona

import retrofit2.Call;
import retrofit2.http.POST;

public interface TokenService {
    @POST("token")
    Call<RefreshTokenResponse> getNewAccessToken(@retrofit2.http.Field("grant_type") String grantType,
                                                      @retrofit2.http.Field("refresh_token") String refreshToken,
                                                      @retrofit2.http.Field("client_id") String clientId,
                                                      @retrofit2.http.Field("client_secret") String clientSecret);
}

// Exemplo de uso
new Retrofit.Builder()
    .baseUrl("https://auth.example.com/")
    .build()
    .create(TokenService.class)
    .getNewAccessToken("refresh_token", "refreshToken", "clientId", "clientSecret")
    .enqueue(new Callback<RefreshTokenResponse>() {
        @Override
        public void onResponse(Call<RefreshTokenResponse> call, Response<RefreshTokenResponse> response) {
            // Handle success
        }

        @Override
        public void onFailure(Call<RefreshTokenResponse> call, Throwable t) {
            // Handle error
        }
    });

const fetch = require('node-fetch');

async function getNewAccessToken(refreshToken, clientId, clientSecret) {
  const response = await fetch('https://auth.example.com/token', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    body: new URLSearchParams({
      grant_type: 'refresh_token',
      refresh_token: refreshToken,
      client_id: clientId,
      client_secret: clientSecret,
    }).toString(),
  });
  const data = await response.json();
  return data;
}

// Exemplo de uso
getNewAccessToken('refreshToken', 'clientId', 'clientSecret').then(console.log).catch(console.error);