curl --request GET \
  --url https://api.withflex.com/v1/promo_codes \
  --header 'Authorization: Bearer <token>'

{
  "promo_codes": [
    {
      "promo_code_id": "fpromo_01jvajb0gcvgxn5d42cqjjmf41",
      "code": "SUMMER2016",
      "coupon": {
        "coupon_id": "fcoup_1234567890",
        "amount_off": 100,
        "applies_to": null,
        "duration": "once",
        "duration_in_months": null,
        "metadata": {
          "key": "value"
        },
        "name": "Coupon",
        "percent_off": 10,
        "max_redemptions": 100,
        "times_redeemed": 0,
        "valid": true,
        "created_at": "2025-05-15T18:12:07.308953Z",
        "test_mode": true
      },
      "max_redemptions": 100,
      "times_redeemed": 0,
      "created_at": "2025-05-15T18:12:07.309203Z",
      "customer": "fcus_01HACM7FZ1084XB1GB6053VM0D",
      "active": true,
      "metadata": {
        "key": "value"
      },
      "test_mode": false
    }
  ]
}