Retrieve a plan

curl -X GET "https://api.live.paisr.tech/v2/plans/{plan_id}" \
  -H "Authorization: Bearer <access_token>" \
  -H "User-Agent: MyApp/1.0" \
  -H "Content-Type: application/json"

{
  "success": true,
  "data": {
    "id": "pln_123456",
    "title": "Premium Service",
    "summary": "Get started with using our premium service.",
    "type": "standard",
    "currency": "SRD",
    "created_at": "2024-01-15T10:30:00Z",
    "options": [
      {
        "id": "plo_123456",
        "description": "Monthly",
        "active": true,
        "unit_price": 9.99,
        "billing_interval": 30,
        "subscribers": 10,
        "attributes": {},
        "created_at": "2024-01-15T10:30:00Z"
      }
    ]
  }
}