[REQ] [rust-axum] Implement some Proptesting Scheme for the Models behind a feature

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

When building a web application I would like to do some proptesting, or more generally just generate a few sample objects to test stuff with. For now this is pretty tedious, since I cannot implement (i.e.) quickcheck::Arbitrary and Shrink for any of the models. This would have to be done in the generated openapi crate. Instead I have to implement newtypes for every single object, essentially recreating the generated models from scratch.

Describe the solution you'd like

What I would like to see is a proptest feature that enables arbitrary/shrink implementations for the models. Whether one would rely on quickcheck or proptest or another solution is secondary.

Describe alternatives you've considered

What I also thought one could do is break out the model definitions into its own crate that could be versioned (and modified by me) with a lesser footprint. However I think the proptesting use case is common enough that this could be it's own feature.

Start by locating the rust-axum generator templates and the generated model definitions. Check how feature flags and model traits are currently emitted, then review existing Rust generator tests before deciding how a proptest-related feature should cover arbitrary and shrink behavior. Done means the feature can generate usable model implementations without requiring newtypes.