[BUG] go-gin-server generates empty struct for inappropriate types

[coryschwartz]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Switching from go-server to go-gin-server, I am surprised to see invalid models generated. I'm unable to switch to the gin server without manually editing the code after generation.

openapi-generator version

% ./tools/openapi-generator-cli version
7.4.0

OpenAPI declaration file content or url

bug is demonstrated in gist:
https://gist.github.com/coryschwartz/4b3674d8493e3398be9858993efa57f6

Generation Details

Empty struct is generated regardless of the type of model required in the yaml file. In my case,
I'm trying to generate models with a list of strings and a string map with "additional attributes", and the generated code is unusable since they are just an empty struct.

Steps to reproduce

Start with openapi yaml file with a list of strings defined.
Generate with go-gin-server
Observe that list of strings and string map are generated as empty structs

If you use my demo gist, you can run "make generate"

Related issues/PRs

There are a couple PRs related to improving the go-gin-server template, although not directly to empty struct generation.

#7280
#10429

Suggest a fix

The mustache file in question is this one: https://github.com/OpenAPITools/openapi-generator/blob/v7.4.0/modules/openapi-generator/src/main/resources/go-gin-server/model.mustache

This template lacks features that are found in the go-server template -- particularly the primitive type generation. I suspect a lot of the go-server model could be re-used in the go-gin-server template.

I'd be willing to sponsor the work.