curl --request POST \
  --url "https://api.harmonyforstaffing.com/oauth/token" \
  --header 'Content-Type: application/x-www-form-urlencoded' \
  --data-urlencode "grant_type=refresh_token" \
  --data-urlencode "refresh_token=def50200641f3e..." \
  --data-urlencode "client_id=your_client_id" \
  --data-urlencode "client_secret=your_client_secret"

{
  "access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "token_type": "Bearer",
  "expires_in": 86400,
  "refresh_token": "def50200641f3e...",
  "scope": "read write"
}