curl --request POST \
  --url https://api.pocketflows.com/email_templates/{id}/send \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data '{
  "from": "<string>",
  "attachments": [
    {
      "content": "<string>",
      "name": "<string>"
    }
  ],
  "to": "<string>",
  "variables": {}
}'

{
  "id": "<string>",
  "created_at": "<string>",
  "customer": "<string>",
  "subject": "<string>",
  "sent_at": "<string>",
  "failed_at": "<string>",
  "failed_reason": "<string>",
  "to_email_address": "<string>",
  "sendgrid_message_id": "<string>",
  "paubox_message_id": "<string>",
  "postmark_message_id": "<string>",
  "ok": true
}