Query should add support for non-constant defaultValue

[techouse]

I noticed that there was a discussion around this already in #21 and the proposed solution added a defaultValue option to Query.

class Query {
  final String name;
  final dynamic defaultValue;
  ...
}

I recently found myself in need in need of such a feature when defaulting to a value of a function call, e.g. DateTime.now(). toIso8601String().

Currently, there's no other way of doing this other than making the auto-generated method private and wrapping it in another method and supplying the dynamic data within that function's body, just like it's explained here.

[techouse]

Never mind, I figured I could just get by by using a @FactoryConverter(request: doSomethingToTheParams).