Add a new waitlist

curl --request POST \
  --url https://api.letraz.app/api/v1/waitlist/ \
  --header 'Content-Type: application/json' \
  --data '{
  "email": "jsmith@example.com",
  "referrer": "<string>"
}'

{
  "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "email": "jsmith@example.com",
  "referrer": "<string>",
  "waiting_number": 123,
  "created_at": "2023-11-07T05:31:56Z"
}