curl --request POST \
  --url http://localhost/public/v1/email/contacts/unsubscribe \
  --header 'Content-Type: application/json' \
  --data '
{
  "email": "jsmith@example.com",
  "reason": "<string>"
}
'

{
  "ok": true,
  "email": "<string>",
  "unsubscribed_at": "<string>",
  "reason": "<string>"
}