List all ACH mandates

curl --request GET \
  --url https://commerce1.on-hellgate.dev/customers/{customer_id}/ach-mandates \
  --header 'X-API-Key: <api-key>'

{
  "data": [
    {
      "account_holder": "<string>",
      "account_number": "<string>",
      "account_type": "<string>",
      "country_code": "<string>",
      "email": "<string>",
      "routing_number": "<string>",
      "status": "<string>",
      "token": "<string>"
    }
  ],
  "pagination": {
    "current_page": 123,
    "next_page": 123,
    "page_size": 123,
    "previous_page": 123,
    "total_items": 123,
    "total_pages": 123
  }
}