Add a param converter and DTO for XB data model

Methods such as those in ClientServerConversionTrait have logic around converting incoming request bodies into Typed data objects but also mix in some validation results

All of that is a stop-gap solution, the top priority should be resolving 🐛 Some components cannot be used in XB because UI prevents SDC props being named `name` Active , to evolve the client-side data model to support all known (current and ideally also future) needs.

@larowlan Do you agree with resolving that issue first? I've started the conversations for that in the week before my paternity leave, to set the stage, but it has unfortunately not been followed through. 😞

Seems reasonable to me