[REQ] builder-pattern for model beans

[davidkarlsen]

Is your feature request related to a problem? Please describe.

Generated model beans are plain beans - these are not so nice to work with vs builder-based beans.

Describe the solution you'd like

Have builders for model beans, builders in general and optionally use http://immutables.io .

Describe alternatives you've considered

Plain builders can probably just be implemented with plain code, or use something like immutables.io.

Additional context

I use java, I use the maven plugin, and the generator flavour for jaxrs cxf.