{
  "listenPort": ["required", "positive_integer"],
  "apiPath": ["required", "url"],
  "staticUrl": ["required", "url"],
  "mainPage": ["required", "url"],
  "mail": ["required", {"nested_object": {
    "from": ["required", "string"],
    "transport": ["required", {"one_of": ["SMTP", "SENDMAIL"] }],
    "auth": {"nested_object": {
      "user": ["required", "string"],
      "pass": ["required", "string"]
    }}
  }}]
}