Retrieve a promo code

{  "id": "string",  "object": "promocode",  "code": "string",  "type": "string",  "percent_off": 0,  "amount_off": 0,  "currency": "eur",  "usage_limit": 0,  "times_used": 0,  "is_active": true,  "is_valid": true,  "valid_from": "string",  "valid_until": "string",  "events": [    "string"  ],  "ticket_types": [    "string"  ],  "created_at": "string",  "updated_at": "string"}