[Go] Fix deepObject serialization that are anyOf

[tanmaykm]

Updates the go client generator to have the generated struct for anyOf types conform to MappedNullable interface. Fixes query params serialization for deepObjects that are of anyOf type.

Implements the suggestion in #19085

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• Read the contribution guidelines.
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  Commit all changed files.
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cc: @wing328 @antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04) @lwj5 (2023/04)

[wing328]

thanks for the PR

can you please review the test failure when you've time?

https://app.circleci.com/pipelines/github/OpenAPITools/openapi-generator/30391/workflows/356f8074-0c40-4353-9c03-8a1efa9cdc6a/jobs/98609

[tanmaykm]

Thanks @wing328 for taking a look.
The test failures are now resolved.

[tanmaykm]

Does this look good now @wing328 ?

[wing328]

can you please add a test or 2 to modules/openapi-generator/src/test/resources/3_0/go/petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml and regenerate the samples?

[tanmaykm]

@wing328 added tests to petstore-with-fake-endpoints-models-for-testing-with-http-signature.yaml in c8b07f7

[tanmaykm]

@wing328 is there anything else needed?

[wing328]

nope. let's give it a try

thanks for the PR