[GoServer] Generate non-required parameters as pointers (nil-able)

[phil-bugdahn-hs]

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This PR fixes #19169

The problem is that, using an OpenAPI spec that specifies a non-required query param, the go-server generator will generate the server handler taking that parameter as a value rather than a pointer. By doing this, it is not possible to tell in the handler whether the parameter was actually passed or if it is just a default value. By using a pointer the parameter value will be nil if not passed by the client. This PR should fix that issue.

[wing328]

@phil-bugdahn-hs thanks for the PR. can you please review the test failure when you've time?

https://github.com/OpenAPITools/openapi-generator/actions/runs/9941343559/job/27462431755?pr=19149

[wing328]

cc
@antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04) @lwj5 (2023/04)

[phil-bugdahn-hs]

Hi @wing328, thanks for your response. I think I have resolved the test issue.

[wing328]

@phil-bugdahn-hs thanks again for the PR.

Is it correct to say that this is a breaking change (without fallback)?

[lwj5]

Hi @phil-bugdahn-hs, I think the problem has been discussed in #16980 and #17051. You may want to review the pointers there.

Is this PR trying to do what is stated in #17321?

Required and Nullable are orthogonal concepts. I don't think this PR should be merged

[phil-bugdahn-hs]

Closing as per disccusion in the issue.