curl --request POST \
  --url https://api-v2.missioninbox.com/billing/attach_payment_method/ \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '{
  "payment_method_id": "<string>"
}'

{
  "success": true,
  "payment_method_id": "<string>"
}