[REQ] [Dart] Models as value types #3797
Description
Is your feature request related to a problem? Please describe.
I would like to be able to have the generator produce models that are value types with features like immutability, state based equivalence and deep clone / copyWith.
Describe the solution you'd like
Describe alternatives you've considered
The openapitools generator could just add an overload of == and hashMap and a copyWith function to each model, but there are other benefits of built_value and (imo) it is a better option. It does require an extra code gen step though, and has the weird dart source_gen syntax so I'm sure it's not everyone's cup of tea.
Additional context
I don't know if this is something others would want but I plan to implement this for myself so I thought I would create an issue for discussion.