[BUG] [Go] Free-form query parameters are not serialized correctly

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

The OpenAPI 3.x schema describes a way to specify arbitrary query parameters using "free-form query parameters" (the linked page doesn't have good anchors so you'll have to search for the quoted text on that page to see the example in situ).

Given the following example from the page linked above:

in: query
name: freeForm
schema:
  type: object
  additionalProperties:
    type: string
style: form

If I generate a Go client and use that client to send a request with freeForm := map[string]string{"search":"something"}, the client should send a request to the API that looks roughly like this:

https://example.com/api/endpoint?search=something

but instead the client sends a request that looks like this:

https://example.com/api/endpoint?freeForm[search]=something.

Based on the OpenAPI specification for serializing query parameters it appears that generated Go clients use deepObject-style serialization for query parameters that are objects, even if a different serialization (in this case, form) is specified.

openapi-generator version

v6.6.0

OpenAPI declaration file content or url

TODO: Working on filling in the remaining fields but wanted to get the issue filed sooner rather than later.

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

TODO but I think this would be localized to the generated parameterAddToHeaderOrQuery function

Start with the generated Go client's parameterAddToHeaderOrQuery function and reproduce the free-form query parameter example described in the issue. Compare the requested form serialization with the observed deepObject-style output; done means a map such as {"search":"something"} produces ?search=something, with a focused regression test for the behavior.