Config parameters that have defaults should be optional

When a config parameter has a default value, the user should be able to optionally omit it from the config file.

For example, since playgroundEnabled has a default value of true, the user need not specify it.

Currently, the server throws an exception for missing parameters.

[hrj]

The defaults can be what is inside the automatically created config file:

{
  "randomSeed" : some random integer,
  "port" : 8888,
  "address" : "0.0.0.0",
  "captchaExpiryTimeLimit" : 5,
  "throttle" : 1000,
  "threadDelay" : 2,
  "playgroundEnabled" : true,
  "corsHeader" : "",
  "maxAttempts" : 10,
}

[hrj]

Ideally, we shouldn’t change the type because it will break existing configurations.

I have added a suggestion to the PR, please have a look.