Reads all Allowance incidences

Example response

{
  "data": [
    {
      "id": "1",
      "employee_id": "1",
      "description": "Added because working on a holiday",
      "days_in_cents": 100,
      "timeoff_allowance_id": "2",
      "effective_on": "2024-01-02",
      "target_balance": "accrued",
      "created_at": 1723623354,
      "updated_at": 1723623354
    }
  ]
}