Mapbackeds: Optionally enforce strictly all fields and/or default values

[kaifox]

As an option to the builder, one could imagine something like:

builder(Person.class).requireAllFields().....

A corresponding check in the builder (or constructor), could throw if not all fields are set during building time.

Or, if we allow nulls, we could at least prevent throwing because of the cast to primitives (which never can be null):

builder(Person.class).primitiveDefaults().... // would e.g. return 0 for int, 0.0 for double, 

One could even have more advanced default values something like:

builder(Person.class).defaultsWherePossible().... // would e.g. return (additionally to above) "" for string, empty lists for lists ... etc

Also something like

builder(Person.class).defaults(Function<Class<T>, T> defaultFactory).... 

could be imagined ...

All to be implemented as soon as we need it ;-)