Add cars to a Billing Account

curl --request POST \
  --url https://fleet.staging.ezprk.dev/api/billing-accounts/{baId}/cars \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "licenseNumbers": [
    "<string>"
  ]
}
'

{
  "failures": [
    {
      "licenseNumber": "<string>",
      "error": "<string>"
    }
  ]
}