curl --request POST \
  --url https://api.sandbox.monite.com/v1/mail_templates/{template_id}/make_default \
  --header 'Authorization: Bearer <token>' \
  --header 'x-monite-version: <x-monite-version>'

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "created_at": "2023-11-07T05:31:56Z",
  "updated_at": "2023-11-07T05:31:56Z",
  "body_template": "<string>",
  "is_default": true,
  "language": "<string>",
  "name": "<string>",
  "subject_template": "<string>",
  "type": "<string>"
}