curl --request PATCH \
  --url https://api.railmail.app/api/v1/subscribers/{email} \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "firstName": "<string>",
  "lastName": "<string>",
  "phone": "<string>",
  "customFields": {}
}
'

{
  "subscriberKey": "<string>",
  "email": "jsmith@example.com",
  "firstName": "<string>",
  "lastName": "<string>",
  "phone": "<string>",
  "status": "<string>",
  "source": "<string>",
  "createdAt": "2023-11-07T05:31:56Z",
  "updatedAt": "2023-11-07T05:31:56Z"
}