curl --request PATCH \
  --url https://app.herondata.io/api/email_templates/{heron_id} \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '{
  "cc_address": null,
  "html_body": "<string>",
  "name": "<string>",
  "reply_to_address": null,
  "to_address": null
}'

{
  "email_template": {
    "cc_address": null,
    "heron_id": "<string>",
    "html_body": "<string>",
    "name": "<string>",
    "reply_to_address": null,
    "to_address": null
  }
}