Create an ACH mandate

curl --request POST \
  --url https://commerce1.on-hellgate.dev/customers/{customer_id}/ach-mandates \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "account_holder": "<string>",
  "account_number": "<string>",
  "account_type": "<string>",
  "routing_number": "<string>",
  "country_code": "<string>",
  "email": "<string>"
}
'

{
  "account_holder": "<string>",
  "account_number": "<string>",
  "account_type": "<string>",
  "country_code": "<string>",
  "email": "<string>",
  "routing_number": "<string>",
  "status": "<string>",
  "token": "<string>"
}