Created by: jacob-pro
Resolves https://github.com/OpenAPITools/openapi-generator/issues/13453
This was a regression in https://github.com/OpenAPITools/openapi-generator/pull/13231 - I didn't realise that this was a feature / pattern being used.
Test cases have been added (in both Java and specs) so that this shouldn't happen again.
(Also cleans up a couple of dead/unused Rust codegen files from 2019)
@wing328 @siketyan