Create an email registration

curl --request POST \
  --url https://api.oneofnone.io/v1/registrations/register-email \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "email": "jsmith@example.com",
  "collection_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "short_url": "<string>",
  "user_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "metadata": {}
}
'

{
  "success": true,
  "email": "<string>",
  "registration_id": "<string>",
  "token_id": 123,
  "registration_settings": {}
}