const response = await fetch('https://api.commune.email/oauth/token', {
  method: 'POST',
  headers: {
    'Authorization': `Basic ${credentials}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    grant_type: 'refresh_token',
    refresh_token: storedRefreshToken,
  }),
});

const data = await response.json();
// IMPORTANT: Save the new refresh_token — the old one is now invalid

resp = httpx.post(
    'https://api.commune.email/oauth/token',
    headers={
        'Authorization': f'Basic {credentials}',
        'Content-Type': 'application/json',
    },
    json={
        'grant_type': 'refresh_token',
        'refresh_token': stored_refresh_token,
    },
)

data = resp.json()
# Save data['refresh_token'] — old one is invalid

curl -X POST https://api.commune.email/oauth/token \
  -H "Authorization: Basic $(echo -n 'comm_client_xxx:comm_secret_xxx' | base64)" \
  -H "Content-Type: application/json" \
  -d '{"grant_type": "refresh_token", "refresh_token": "comm_refresh_xxx..."}'

{
  "access_token": "comm_oauth_new...",
  "token_type": "Bearer",
  "expires_in": 3600,
  "refresh_token": "comm_refresh_new...",
  "id_token": "eyJhbGciOi...",
  "agent_id": "agt_4f3a9b2c1d7e8a9b",
  "scope": "identity"
}