[REQ] Generate Constructor with Required Args Only

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

The problem is mapstruct defaults to using no arg constructor when there are multiple constructors. Mapstruct can use a particular constructor if it is annotated with something (forget but can look up)

Describe the solution you'd like

Instead of adding the annotation that is specific to mapstruct, I would like a way to only use the required arguments constructor generated by openapi. This is also more typesafe as it tells me what fields are required

Describe alternatives you've considered

Looked into available config options and did not see what would be helpful

Additional context

The issue names no files, tests, or generator entry point. First identify which Java generator and model templates control constructor generation, then clarify how required arguments should be defined and tested. Done means generated models expose a required-arguments constructor that supports the requested MapStruct use case without extra annotations.